Document:

Exhibit 10.22

THE SECURITIES REPRESENTED BY THIS WARRANT HAVE BEEN ACQUIRED FOR INVESTMENT AND
HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED ("1933
ACT") OR ANY STATE SECURITIES LAWS. SUCH SECURITIES MAY NOT BE SOLD OR
TRANSFERRED IN THE ABSENCE OF SUCH REGISTRATION OR AN EXEMPTION THEREFROM UNDER
THE 1933 ACT AND ANY APPLICABLE STATE SECURITIES LAWS.

                           WARRANT TO PURCHASE SHARES
                                 OF THE STOCK OF
                          INFORMEDIX ACQUISITION CORP.
                   (Void after Expiration Date-August 1, 2008)

     This certifies that Allied International Fund or its successors or assigns
("Holder") in consideration of one cent in hand paid for each share of the
Common Stock exercised hereunder, shall be entitled to purchase from InforMedix
Acquisition Corp., a Delaware corporation ("Company"), having its principal
place of business at 5880 Hubbard Drive, Rockville, MD 20852, Fifty Thousand
(50,000) shares of fully paid and nonassessable shares of the Company's common
stock ("Common Stock"), at an exercise price of one dollar and fifty cents
($1.50) per share ("Exercise Price"). This Warrant shall be exchangeable for
shares at any time, or from time-to-time, up to and including 5:00 p.m. (local
time) on the fifth anniversary from the date of this Warrant, namely, August 1,
2008 ("Expiration Date"), upon the surrender to the Company at its principal
place of business (or at such other location as the Company may advise the
Holder in writing) of this Warrant properly endorsed with a form of subscription
in substantially the form attached hereto duly filled in and signed and, if
applicable, upon payment in cash or by check of the aggregate Exercise Price for
the number of shares for which this Warrant is being exercised determined in
accordance with the provisions hereof. The Exercise Price and the number of
shares of Common Stock purchasable hereunder are subject to adjustment as
provided in Section 2 of this Warrant.

1.   Exercise; Issuance of Certificates; Payment for Shares.

     1.1  General. This Warrant is exercisable in full on one (1) occasion only,
          at the option of the Holder of record at any time or from time, to
          time, up to the Expiration Date for all of the shares of Common Stock
          (but not for a fraction of a share) which may be purchased hereunder.
          The Company agrees that the shares of Common Stock purchased under
          this Warrant shall be and are deemed to be issued to the Holder hereof
          as the record owner of such shares as of the close of business on the
          date on which this Warrant shall have been surrendered, properly
          endorsed, the completed, executed Subscription Form (attached hereto
          as Exhibit A-1) delivered and payment made for such shares.
          Certificates for the shares of Common Stock so purchased, together
          with any other securities or property to which the Holder is entitled
          upon such exercise, shall be delivered to the Holder by the Company at
          the Company's expense within a reasonable time after the rights
          represented by this Warrant have been

<PAGE>

          so exercised, and in any event, within fifteen (15) days of such
          exercise. Each Common Stock certificate so delivered shall be in such
          denominations of Common Stock as may be requested by the Holder hereof
          and shall be registered on the Company's books in the name designated
          by such Holder.

     1.2  Net Issue Exercise. Notwithstanding any provisions herein to the
          contrary, if the fair market value of one share of the Company's
          Common Stock is greater than the Exercise Price (at the date of
          calculation as set forth below), in lieu of exercising this Warrant
          for cash, the Holder may elect to receive shares equal to the value
          (as determined below) of this Warrant (or the portion thereof being
          canceled) by surrender of this Warrant at the principal office of the
          Company together with the properly endorsed Form of Subscription and
          notice of such election in which event the Company shall issue to the
          Holder a number of shares of Common Stock computed using the following
          formula:

                                   X = Y (A-B)
                                       -------
                                          A

     Where X= the number of shares of Common Stock to be issued to the Holder

          Y=    the number of shares of Common Stock purchasable under the
                Warrant or, if only a portion of the Warrant is being exercised,
                the portion of the Warrant being canceled (at the date of such
                calculation)

          A=    the fair market value of one share of Common Stock (at the date
                of such calculation)

          B=    Exercise Price (as adjusted to the date of such calculation).

         For purposes of the above calculation, the fair market value of one
         share of Common Stock shall be determined by the Company's Board of
         Directors in good faith; provided, however, that where there is a
         public market for the Common Stock, the fair market value per share
         shall be the average of the closing prices of the Common Stock quoted
         on the Bulletin Board, Nasdaq National Market (or similar system), or
         on any exchange on which the Common Stock is listed, whichever is
         applicable, over the five (5) day period ending one (1) day before the
         day the current fair market value is being determined.

          1.3  SHARES TO BE FULLY PAID; RESERVATION OF SHARES. The Company
               covenants and agrees that all shares of Common Stock which may be
               issued upon the exercise of the rights represented by this
               Warrant will, upon issuance, be duly authorized, validly issued,
               fully paid and nonassessable and free from all preemptive rights
               of any shareholder and free of all taxes, liens and charges with
               respect to the issue thereof. The Company further covenants and
               agrees that, during the period within which the rights
               represented by this Warrant may be exercised, the

                                      -2-
<PAGE>

               Company will at all times have authorized and reserved, for the
               purpose of issue or transfer upon exercise of the subscription
               rights evidenced by this Warrant, a sufficient number of shares
               of authorized but unissued Common Stock, when and as required to
               provide for the exercise of the rights represented by this
               Warrant. The Company will take all such action as may be
               necessary to assure that such shares of Common Stock may be
               issued as provided herein without violation of any applicable law
               or regulation, or of any requirements of any domestic securities
               exchange upon which the Common Stock or other securities may be
               listed; provided, however, that the Company shall not be required
               to effect a registration under federal or state securities laws
               with respect to such exercise. The Company will not take any
               action which would result in any adjustment of the Exercise Price
               (as set forth in Section 2 hereof) if the total number of shares
               of Common Stock issuable after such action upon exercise of all
               outstanding warrants, together with all shares of Common Stock
               then outstanding and all shares of Common Stock then issuable
               upon exercise of all options and upon the conversion of all
               convertible securities then outstanding, would exceed the total
               number of shares of Common Stock or Equity Securities then
               authorized by the Company's Articles/Certificate of Incorporation
               ("Company Charter").

2. DETERMINATION OR ADJUSTMENT OF EXERCISE PRICE AND NUMBER OF SHARES. The
Exercise Price and the number of shares purchasable upon the exercise of this
Warrant shall be subject to adjustment from time to time upon the occurrence of
certain events described in this Section 2. Upon each adjustment of the Exercise
Price, the Holder of this Warrant shall thereafter be entitled to purchase, at
the Exercise Price resulting from such adjustment, the number of shares obtained
by multiplying the Exercise Price in effect immediately prior to such adjustment
by the number of shares purchasable pursuant hereto immediately prior to such
adjustment, and dividing the product thereof by the Exercise Price resulting
from such adjustment. The initial number of shares purchasable upon the exercise
of this Warrant is One Hundred Seventy Thousand (170,000) shares.

     2.1  Subdivision or Combination of Common Stock. In case the Company shall
          at any time subdivide its outstanding shares of Common Stock into a
          greater number of shares, the Exercise Price in effect immediately
          prior to such subdivision shall be proportionately reduced, and
          conversely, in case the outstanding shares of Common Stock of the
          Company shall be combined into a smaller number of shares, the
          Exercise Price in effect immediately prior to such combination shall
          be proportionately increased.

     2.2  2.2 Dividends in Common Stock, Other Stock, Property,
          Reclassification. If at any time or from time to time the holders of
          Common Stock (or any shares of stock or other securities at the time
          receivable upon the exercise of this Warrant or into which such
          securities are convertible) shall have received or become entitled to
          receive, without

                                      -3-
<PAGE>

     payment therefore.

          2.2.1 Stock, Common Stock or any shares of stock or other securities
                which are at any time directly or indirectly convertible into
                or exchangeable for Common Stock, or any rights or options to
                subscribe for, purchase or otherwise acquire any of the
                foregoing by way of dividend or other distribution,

          2.2.2 Any cash paid or payable otherwise than as a cash dividend, or

          2.2.3 Stock, Common Stock or additional stock or other securities or
                property (including cash) by way of spinoff, split-up,
                reclassification, combination of shares or similar corporate
                rearrangement, (other than shares of Common Stock issued as a
                stock split or adjustments in respect of which shall be covered
                by the terms of Section 2.1 above), then and in each such case,
                the Holder hereof shall, upon the exercise of this Warrant, be
                entitled to receive, in addition to the number of shares of
                Stock or Common Stock receivable thereupon, and without payment
                of any additional consideration therefor, the amount of stock
                and other securities and property (including cash in the cases
                referred to in clause (2.2.2) above and this clause (2.2.3))
                which such Holder would hold on the date of such exercise had
                he been the holder of record of such Common Stock as of the date
                on which holders of Common Stock received or became entitled to
                receive such shares or all other additional stock and other
                securities and property.

     2.3  Reorganization, Reclassification, Consolidation, Merger or Sale. If
          any recapitalization, reclassification or reorganization of the
          capital stock of the Company, or any consolidation or merger of the
          Company with another corporation, or the sale of all or substantially
          all of its assets or other transaction shall be effected in such a way
          that holders of Common Stock shall be entitled to receive stock,
          securities, or other assets or property (an "Organic Change"), then,
          as a condition of such Organic Change, lawful and adequate provisions
          shall be made by the Company whereby the Holder hereof shall
          thereafter have the right, upon exercise of this warrant, to purchase
          and receive (in lieu of the shares of the Common Stock of the Company
          immediately theretofore purchasable and receivable upon the exercise
          of the rights represented by this Warrant) such shares of stock,
          securities or other assets or property as may be issued or payable
          with respect to or in exchange for a number of outstanding shares of
          such Common Stock equal to the number of shares of such stock
          immediately theretofore purchasable and receivable upon the exercise
          of the rights represented by this Warrant. In the event of any Organic
          Change, appropriate provision shall be made by the Company with
          respect to the rights and interests of the Holder of this Warrant to
          the

                                      -4-
<PAGE>

          end that the provisions hereof (including, without limitation,
          provisions for adjustments of the Exercise Price and of the number of
          shares purchasable and receivable upon the exercise of this Warrant)
          shall thereafter be applicable, in relation to any shares of stock,
          securities or assets thereafter deliverable upon the exercise hereof.
          The Company will not effect any such consolidation, merger or sale
          unless, prior to the consummation thereof, the successor corporation
          (if other than the Company) resulting from such consolidation or the
          corporation purchasing such assets shall assume by written instrument
          reasonably satisfactory in form and substance to the Holder executed
          and mailed or delivered to the registered Holder hereof at the last
          address of such Holder appearing on the books of the Company, the
          obligation to deliver to such Holder, upon Holder's exercise of this
          Warrant and payment of the purchase price in accordance with the terms
          hereof, such shares of stock, securities or assets as, in accordance
          with the foregoing provisions, such Holder may be entitled to
          purchase.

     2.4  Certain Events. If any change in the outstanding Common Stock of the
          Company or any other event occurs as to which the other provisions of
          this Section 2 are not strictly applicable or if strictly applicable
          would not fairly protect the purchase rights of the Holder of the
          Warrant in accordance with such provisions, then the Board of
          Directors of the Company shall make an adjustment in the number and
          class of shares available under the Warrant, the Exercise Price or the
          application of such provisions, so as to protect such purchase rights
          as aforesaid. The adjustment shall be such as will give the Holder of
          the Warrant upon exercise for the same aggregate Exercise Price the
          total number, class and kind of shares as he would have owned had the
          Warrant been exercised prior to the event and had he continued to hold
          such shares until after the event requiring adjustment.

     2.5  Notices of Change.

          2.5.1 Upon any determination or adjustment in the number or class of
                shares subject to this Warrant and of the Exercise Price, the
                Company shall give written notice thereof to the Holder,
                setting forth in reasonable detail and certifying the
                calculation of such determination or adjustment.

          2.5.2 The Company shall give written notice to the Holder at least 10
                business days prior to the date on which the Company closes its
                books or takes a record for determining rights to receive any
                dividends or distributions.

          2.5.3 The Company shall also give written notice to the Holder at
                least 30 business days prior to the date on which an Organic
                Change shall take place.

                                      -5-
<PAGE>

3. ISSUE TAX. The issuance of certificates for shares of Common Stock upon the
exercise of the Warrant shall be made without charge to the Holder of the
Warrant for any issue tax (other than any applicable income taxes) in respect
thereof; provided, however, that the Company shall not be required to pay any
tax which may be payable in respect of any transfer involved in the issuance and
delivery of any certificate in a name other than that of the then Holder of the
Warrant being exercised.

4. CLOSING OF BOOKS. The Company will at no time close its transfer books
against the transfer of any warrant or of any shares of stock issued or issuable
upon the exercise of any warrant in any manner which interferes with the timely
exercise of this Warrant.

5. NO VOTING OR DIVIDEND RIGHTS; LIMITATION OF LIABILITY. Nothing contained in
this Warrant shall be construed as conferring upon the Holder hereof the right
to vote as a shareholder of the Company. No dividends or interest shall be
payable or accrued in respect of this Warrant, the interest represented hereby,
or the shares purchasable hereunder until, and only to the extent that, this
Warrant shall have been exercised. The Holder of this Warrant shall receive all
notices as if a shareholder of the Company. No provisions hereof, in the absence
of affirmative action by the Holder to purchase shares of Common Stock, and no
mere enumeration herein of the rights or privileges of the Holder hereof, shall
give rise to any liability of such Holder for the Exercise Price or as a
shareholder of the Company, whether such liability is asserted by the Company or
by its creditors.

6. RIGHTS AND OBLIGATIONS SURVIVE EXERCISE OF WARRANT. The rights and
obligations of the Company, of the Holder of this Warrant and of the holder of
shares of Common Stock issued upon exercise of this Warrant, shall survive the
exercise of this Warrant.

7.   Further Representations, Warranties and Covenants of the Company.

     7.1  Articles and Bylaws. The Company has made available to Holder true,
          complete and correct copies of the Company Charter and Bylaws, as
          amended, through the date hereof.

     7.2  Due Authority. The execution and delivery by the Company of this
          Warrant and the performance of all obligations of the Company
          hereunder, including the issuance to Holder of the right to acquire
          the shares of Common Stock, have been duly authorized by all necessary
          corporate action on the part of the Company, and the Warrant is not
          inconsistent with the Company Charter or Bylaws and constitutes a
          legal, valid and binding agreement of the Company, enforceable in
          accordance with its terms.

     7.3  Consents and Approvals. No consent or approval of, giving of notice
          to, registration with, or taking of any other action in respect of any
          state, federal or other governmental authority or agency is required
          with respect

                                      -6-
<PAGE>

          to the execution, delivery and performance by the Company of its
          obligations under this Warrant, except for any filing required by
          applicable federal and state securities laws, which filing will be
          effective by the time required thereby.

     7.4  Issued Securities. All issued and outstanding shares of capital stock
          of the Company have been duly authorized and validly issued and are
          fully paid and nonassessable. All outstanding shares of capital stock
          were issued in full compliance with all federal and state securities
          laws.

     7.5  Exempt Transaction. Subject to the accuracy of the Holders
          representations in Section 8 hereof, the issuance of the Common Stock
          upon exercise of this Warrant will constitute a transaction exempt
          from (i) the registration requirements of Section 5 of the Securities
          Act of 1933, as amended ("1933 Act"), in reliance upon Section 4(2)
          thereof, or upon the applicable exemption under Regulation D. and (ii)
          the qualification requirements of the applicable state securities
          laws.

     7.6  Compliance with Rule 144. At the written request of the Holder, who
          proposes to sell Common Stock issuable upon the exercise of the
          Warrant in compliance with Rule 144 promulgated by the Securities and
          Exchange Commission, the Company shall furnish to the Holder, within
          thirty (30) days after receipt of such request, a written statement
          confirming the Company's compliance with the filing requirements of
          the Securities and Exchange Commission as set forth in such Rule, as
          such Rule may be amended from time to time.

     7.7  Registration. If at any time the Company shall determine to register
          for its own account or the account of others under the Securities Act
          of 1933, as amended (including without limitation pursuant to the
          registration of any shareholder of the Company), any of its equity
          securities, other than on Form S-8 or Form S-4 or their then
          equivalents (a "Piggyback Registration"), it shall send the Holder
          written notice of such determination and, if within fifteen (15) days
          after receipt of such notice, Holder shall so request in writing, the
          Company shall use its diligent efforts to include in such registration
          statement all or any part of the shares of Common Stock or other
          securities issued or issuable upon conversion of this Note
          ("Registrable Shares") that Holder requests to be registered, except
          that if, in connection with any offering involving an underwriting of
          Common Stock to be issued by the Company the managing underwriter
          shall impose a limitation on the number of shares of Common Stock
          which may be included in the registration statement because, in its
          judgment, such limitations necessary to effect an orderly public
          distribution, then the Company shall be obligated to include in such
          registration statement only such limited portion (or none, if so
          required by the managing underwriter) of the Registrable Shares with
          respect to which such holder has requested inclusion hereunder. Except
          as specifically provided herein, all

                                      -7-
<PAGE>

          Registration Expenses incurred in connection with any registration
          under this Section shall be borne by the Company. All Selling Expenses
          incurred in connection with any registrations hereunder, shall be
          borne by the holders of the securities so registered pro rata on the
          basis of the number of shares so registered. For purposes of this
          Section, "Registration Expenses" means all expenses incurred by the
          Company in complying with this Section, including, without limitation,
          all registration and filing fees, printing expenses, fees and
          disbursements of counsel and independent public accountants for the
          company, fees and expenses of listing the securities with the
          securities exchange, fees and expenses (including counsel fees)
          incurred in connection with complying with state securities or "blue
          sky" laws, fees and expenses of one designated counsel for the Holder
          in connection with the registration of Registrable Shares, transfer
          taxes, fees of transfer agents and registrars, costs of any insurance
          which might be obtained, but excluding any Selling Expenses. For
          purposes of this Section, "Selling Expenses" means all underwriting
          discounts and selling commissions applicable to the sale of
          Registrable Shares and the fees and expenses of more than one counsel
          for the Holder in connection with the registration of Registrable
          Shares.

8.   Representations and Covenants of the Holder.

     8.1  This Warrant has been entered into by the Company in reliance upon the
          following representations and covenants of the Holder:

          8.1.1 Investment Purpose. The Warrant or the Common Stock issuable
                upon exercise of the Warrant will be acquired for investment and
                not with a view to the sale or distribution of any part thereof,
                and the Holder has no present intention of selling or engaging
                in any public distribution of the same except pursuant to a
                registration or exemption.

          8.1.2 Private Issue. The Holder understands (i) that the Warrant and
                the Common Stock issuable upon exercise of this Warrant are not
                registered under the 1933 Act or qualified under applicable
                state securities laws on the ground that the issuance
                contemplated by this Warrant will be exempt from the
                registration and qualifications requirements thereof, and (ii)
                that the Company's reliance on such exemption is predicated on
                the representations set forth in this Section 8.

          8.1.3 Disposition of Holders Rights. In no event will the Holder make
                a disposition of the Warrant or the Common Stock issuable upon
                exercise of the Warrant unless and until (i) it shall have
                notified the Company of the proposed disposition, and (ii) if
                requested by the Company, it shall have furnished the Company
                with an opinion of counsel (which counsel may either be inside
                or outside

                                      -8-
<PAGE>

               counsel to the Holder) satisfactory to the Company and its
               counsel to the effect that (A) appropriate action necessary for
               compliance with the 1933 Act has been taken, or (B) an exemption
               from the registration requirements of the 1933 Act is available.
               Notwithstanding the foregoing, the restrictions imposed upon the
               transferability of any of its rights to acquire Common Stock
               issuable on the exercise of such rights do not apply to transfers
               from the beneficial owner of any of the aforementioned securities
               to its nominee or from such nominee to its beneficial owner, and
               shall terminate as to any particular share of stock when (1) such
               security shall have been effectively registered under the 1933
               Act and sold by the Holder thereof in accordance with such
               registration or (2) such security shall have been sold without
               registration in compliance with Rule 144 under the 1933 Act, or
               (3) a letter shall have been issued to the Holder at its request
               by the staff of the Securities and Exchange Commission or a
               ruling shall have been issued to the Holder at its request by
               such Commission stating that no action shall be recommended by
               such staff or taken by such Commission, as the case may be, if
               such security is transferred without registration under the 1933
               Act in accordance with the conditions set forth in such letter or
               ruling and such letter or ruling specifies that no subsequent
               restrictions on transfer are required. Whenever the restrictions
               imposed hereunder shall terminate, as hereinabove provided, the
               Holder or holder of a share of stock then outstanding as to which
               such restrictions have terminated shall be entitled to receive
               from the Company, without expense to such Holder, one or more new
               certificates for the Warrant or for such shares of stock not
               bearing any restrictive legend.

         8.1.4 Financial Risk. The Holder has such knowledge and experience in
               financial and business matters as to be capable of evaluating the
               merits and risks of its investment, and has the ability to bear
               the economic risks of its investment.

         8.1.5 Risk of No Registration. The Holder understands that if the
               Company does not register with the Securities and Exchange
               Commission pursuant to Section 12 of the 1933 Act, or file
               reports pursuant to Section 15(d), of the Securities Exchange Act
               of 1934 ("1934 Act"), or if a registration statement covering the
               securities under the 1933 Act is not in effect when it desires to
               sell (i) the Warrant, or (ii) the Common Stock issuable upon
               exercise of the Warrant, it may be required to hold such
               securities for an indefinite period. The Holder also understands
               that any sale of the Warrant or the Common Stock issuable upon
               exercise of the Warrant which might be made by it in reliance
               upon Rule 144 under the 1933 Act may be made only in accordance
               with the

                                      -9-
<PAGE>

               terms and conditions of that Rule.

         8.1.6 Accredited Investor. The Holder is an "accredited investor"
               within the meaning of Regulation D promulgated under the 1933
               Act.

9. MODIFICATION AND WAIVER. This Warrant and any provision hereof may be
changed, waived, discharged or terminated only by an instrument in writing
signed by the party against which enforcement of the same is sought.

10. NOTICES. Any notice, request or other document required or permitted to be
given or delivered to the Holder hereof or the Company shall be delivered or
shall be sent by certified mail, postage prepaid, to each such Holder at its
address as shown on the books of the Company or to the Company at the address
indicated therefor in the first paragraph of this Warrant or such other address
as either may from time to time provide to the other.

11. BINDING EFFECT ON SUCCESSORS. As provided in Section 2.3 above, this Warrant
shall be binding upon any corporation succeeding the Company by merger,
consolidation or acquisition of all or substantially all of the Company's
assets. All of the obligations of the Company relating to the Common Stock
issuable upon the exercise of this Warrant shall survive the exercise and
termination of this Warrant. All of the covenants and agreements of the Company
shall inure to the benefit of the successors and assigns of the Holder hereof.

12. DESCRIPTIVE HEADINGS AND GOVERNING LAW. The description headings of the
several sections and paragraphs of this Warrant are inserted for convenience
only and do not constitute a part of this Warrant. This Warrant shall be
construed and enforced in accordance with, and the rights of the parties shall
be governed by the laws of the State of Maryland.

13. LOST WARRANTS. The Company represents and warrants to the Holder hereof that
upon receipt of evidence reasonably satisfactory to the Company of the loss,
theft, destruction, or mutilation of this Warrant and, in the case of any such
loss, theft or destruction, upon receipt of an indemnity reasonably satisfactory
to the Company, or in the case of any such mutilation upon surrender and
cancellation of such Warrant, the Company, at its expense, will make and deliver
a new Warrant, of like tenor, in lieu of the lost, stolen, destroyed or
mutilated Warrant.

14. FRACTIONAL SHARES. No fractional shares shall be issued upon exercise of
this Warrant. The Company shall, in lieu of issuing any fractional share, pay
the Holder entitled to such fraction a sum in cash equal to such fraction
multiplied by the then effective Exercise Price.

                                      -10-
<PAGE>

     IN WITNESS WHEREOF, the Company has caused this Warrant to be duly executed
by its officers, thereunto duly authorized this ____ day of ____________, 200_.

                                  InforMedix Acquisition Corp.,
                                  a Delaware corporation

                                  By:   /s/ Bruce Kehr
                                     ----------------------------------
                                     Name:  Bruce Kehr
                                     Title: Chief Executive Officer
ATTEST:

---------------------------------------
               Secretary

                                      -11-
<PAGE>

                                   EXHIBIT A-1

                                SUBSCRIPTION FORM

Date:  _________________, _______

InforMedix Acquisition Corp. - Attn:  President

Ladies and Gentlemen:

     The undersigned hereby elects to exercise the warrant issued to it by
InforMedix Acquisition Corp. ("Company") and dated August 1, 2008, ("Warrant")
and to purchase thereunder __________________________________ shares of the
Common Stock of the Company ("Shares") at a purchase price of ________________
($______) per Share or an aggregate purchase price of __________________
________________ Dollars ($__________) ("Exercise Price").

     The undersigned hereby elects to convert _______________________ percent
(____%) of the value of the Warrant pursuant to the provisions of Section 1.2 of
the Warrant.

     Pursuant to the terms of the Warrant, the undersigned has delivered the
Exercise Price herewith in full in cash or by certified check or wire transfer.

                                     Very truly yours,<PAGE>

                                                                   Exhibit 10.23

                                 PROMISSORY NOTE
<TABLE>
<CAPTION>

------------------ ------------ ------------- ----------- ---------- ------------- ----------- ----------- -----------
    Principal       Loan Date     Maturity     Loan No.     Call      Collateral    Account     Officer     Initials
<S>                <C>           <C>           <C>          <C>       <C>           <C>         <C>         <C>
  $297,500,000     05/18/2001    08/30/2004      9002        4AO         3112       2350106       CRW
------------------ ------------ ------------- ----------- ---------- ------------- ----------- ----------- -----------
</TABLE>

-------------------------------------------------------------------------------
References in the shaded area are for Lender's use only and do not limit the
applicability of this document to any particular loan or item.
-------------------------------------------------------------------------------

BORROWER: INFORMEDIX, INC.                       LENDER: United Bank
          5920 Hubbard Drive                             2071 Chain Bridge Road
          Rockville, MD 20852                            Vienna, VA 22182

===============================================================================
                                IMPORTANT NOTICE
THIS INSTRUMENT CONTAINS A CONFESSION OF JUDGMENT PROVISION WHICH CONSTITUTES A
WAIVER OF IMPORTANT RIGHTS YOU MAY HAVE AS A DEBTOR AND ALLOWS THE CREDITOR TO
OBTAIN A JUDGMENT AGAINST YOU WITHOUT ANY FURTHER NOTICE.
===============================================================================

Principal Amount: $297,500.00                        Date of Note; May 18, 2001

PROMISE TO PAY. INFORMEDIX, INC. ("Borrower") promises to pay to United Bank
("Lender"), or order, in lawful money of the United States of America, the
principal amount of Two Hundred Ninety Seven Thousand Five Hundred & 00/100
Dollars ($297,500.00), together with interest on the unpaid principal balance
from May 18, 2001, until paid in full.

PAYMENT. Subject to any payment changes resulting from changes in the index,
Borrower will pay this loan in accordance with the following payment schedule:

         3 consecutive monthly Interest payments, beginning June 30, 2001, with
         interest calculated on the unpaid principal balances at an interest
         rate of 1.000 percentage points over the index described below; 36
         consecutive monthly principal payments of $8,263.89 each, beginning
         September 30, 2001, with interest calculated on the unpaid principal
         balances at an interest rate of 1.000 percentage points over the Index
         described below; and 36 consecutive monthly interest payments,
         beginning September 30, 2001, with interest calculated on the unpaid
         principal balances at an interest rate of 1.000 percentage points over
         the index described below. Borrower's final payment of $8,263.89 will
         be due on August 30, 2004. This estimated final payment is based on the
         assumption that all payments will be made exactly as scheduled and that
         the Index does not change; the actual final payment will be for all
         principal and accrued interest not yet paid, together with any other
         unpaid amounts under this Note.

The annual interest rate for this Note is computed on a 365/360 basis; that Is,
by applying the ratio of the annual interest rate over a year of 360 days,
multiplied by the outstanding principal balance, multiplied by the actual number
of days the principal balance is outstanding. Borrower will pay Lender at
Lender's address shown above or at such other place as Lender may designate in
writing. Unless otherwise agreed or required by applicable law, payments will be
applied first to accrued unpaid interest, then to principal, and any remaining
amount to any unpaid collection costs and late charges.

VARIABLE INTEREST RATE. The Interest rate on this Note is subject to change from
time to time based on changes in an independent index which is the Prime Lending
Rate as published in the "Money Rates" section of the Wall Street Journal (the
"Index"). The Index is not necessarily the lowest rate charged by Lender on its
loans. If the Index becomes unavailable during the term of this loan, Lender may
designate a substitute Index after notice to Borrower. Lender will tell Borrower
the current index rate upon Borrower's request. Borrower understands that Lender
may make loans based on other rates as well. The interest rate change will not
occur more often than each DAY. The Index currently is 7.000% per annum. The
interest rate or rates to be applied to the unpaid principal balance of this
Note will be the rate or rates set forth above In the "Payment" section. NOTICE:
Under no circumstances will the interest rate on this Note be more than the
maximum rate allowed by applicable law. Whenever increases occur in the interest
rate, Lender, at its option, may do one or more of the following: (a) Increase
Borrower's payments to ensure Borrower's loan will pay off by its original final
maturity date, (b) Increase Borrower's payments to cover accruing interest, Cc)
Increase the number of Borrower's payments, and (d) continue Borrower's payments
at the same amount and increase Borrower's final payment.

<PAGE>

PREPAYMENT. Borrower agrees that all loan fees and other prepaid finance charges
are earned fully as of the date of the loan and will not be subject to refund
upon early payment (whether voluntary or as a result of default), except as
otherwise required by law. Except for the foregoing, Borrower may pay without
penalty all or a portion of the amount owed earlier than ills due. Early
payments will not, unless agreed to by Lender in writing, relieve Borrower of
Borrower's obligation to continue to make payments under the payment schedule.
Rather, they will reduce the principal balance due and may result in Borrower
making fewer payments.

LATE CHARGE. If a payment is 7 days or more late, Borrower will be charged
5.000% of the regularly scheduled payment.

DEFAULT. Borrower will be in default if any of the following happens: (a)
Borrower fails to make any payment when due. (b) Borrower breaks any promise
Borrower has made to Lender, or Borrower falls to comply with or to perform when
due any other term, obligation, covenant, or condition contained in this Note or
any agreement related to this Note, or in any other agreement or loan Borrower
has with Lender. (c) Borrower defaults under any loan, extension of credit,
security agreement, purchase or sales agreement, or any other agreement, in
favor of any other creditor or person that may materially affect any of
Borrower's property or Borrower's ability to repay this Note or perform
Borrower's obligations under this Note or any of the Related Documents. (d) Any
representation or statement made or furnished to Lender by Borrower or on
Borrower's behalf is false or misleading in any material respect either now or
at the time made or furnished. (e) Borrower becomes insolvent, a receiver is
appointed for any part of Borrower's property, Borrower makes an assignment for
the benefit of creditors, or any proceeding is commenced either by Borrower or
against Borrower under any bankruptcy or insolvency laws. (f) Any creditor tries
to take any of Borrower's property on or in which Lender has a lien or security
interest. This includes a garnishment of any of Borrower's accounts with Lender.
(g) Any guarantor dies or any of the other events described in this default
section occurs with respect to any guarantor of this Note. (h) A material
adverse change occurs in Borrower's financial condition, or Lender believes the
prospect of payment or performance of the indebtedness is impaired. (i) Lender
in good faith deems itself insecure.

If any default, other than a default in payment, is curable and if Borrower has
not been given a notice of a breach of the same provision of this Note within
the preceding twelve (12) months, it may be cured (and no event of default will
have occurred) if Borrower, after receiving written notice from Lender demanding
cure of such default: (a) cures the default within fifteen (15) days; or (b) if
the cure requires more than fifteen (15) days, immediately initiates steps which
Lender deems in Lender's sole discretion to be sufficient to cure the default
and thereafter continues and completes all reasonable and necessary steps
sufficient to produce compliance as soon as reasonably practical.

LENDER'S RIGHTS. Upon default, Lender may declare the entire unpaid principal
balance on this Note and all accrued unpaid interest, together with all other
applicable fees, costs and charges, if any, immediately due and payable, without
notice, and then Borrower will pay that amount. Upon default, or If this Note Is
not paid at final maturity, Lender, at its option, may add any unpaid accrued
Interest to principal and such sum will bear interest therefrom until paid, at
the rate provided in this Note. Furthermore, subject to any limits under
applicable law, upon default, Borrower also agrees to pay Lender's attorney fees
equal to _____* of the principal balance due on the Note, and all of Lender's
other collection expenses, whether or not there is a lawsuit and including
without limitation legal expenses or bankruptcy proceedings. This Note shall be
governed by, construed and enforced in accordance with the laws of the
Commonwealth of Virginia.

CONFESSION OF JUDGMENT. Upon a default in payment of the indebtedness at
maturity, whether by acceleration or otherwise, Borrower hereby irrevocably
authorizes and empowers Neil I. Title and Julian Karpoff (either of whom may act
alone) as Borrower's attorney-in-fact to appear in the Arlington County clerk's
office and to confess judgment against Borrower for the unpaid amount of this
Note as evidenced by an affidavit signed by an officer of Lender setting forth
the amount then due, plus attorneys' fees as provided in this Note, plus costs
of suit, and to release all errors, and waive all rights of appeal. if a copy of
this Note, verified by an affidavit, shall have been filed in the proceeding, it
will not be necessary to file the original as a warrant of attorney. Borrower
waives the right to any stay of execution and the benefit of all exemption laws
now or hereafter in effect. No single exercise of the foregoing warrant and
power to confess judgment will be deemed to exhaust the power, whether or not
any such exercise shall be held by any court to be invalid, voidable, or void;
but the power will continue undiminished and may be exercised from time to time
as Lender may elect until all amounts owing on this Note have been paid in full.

<PAGE>

RIGHT OF SETOFF. Borrower grants to Lender a contractual security interest in,
and hereby assigns, conveys, delivers, pledges, and transfers to Lender all
Borrower's right, title and interest in and to, Borrower's accounts with Lender
(whether checking, savings, or some other account), including without limitation
all accounts held jointly with someone else and all accounts Borrower may open
in the future, excluding however all IRA and Keogh accounts, and all trust
accounts for which the grant of a security interest would be prohibited by law.
Borrower authorizes Lender, to the extent permitted by applicable law, to charge
or setoff alt sums owing on this Note against any and all such accounts.

PRIOR NOTE. This PROMISSORY NOTE is a refinance of existing indebtedness between
Borrower and Lender, evidenced by certain credit agreements including but not
limited to the following: a CHANGE IN TERMS AGREEMENT dated February 6, 2000 in
the principal amount of $297,500.00, and a PROMISSORY NOTE dated July 6, 1998 in
the principal amount of $297,500.00.

GENERAL PROVISIONS. Lender may delay or forgo enforcing any of its rights or
remedies under this Note without losing them. Borrower and any other person who
signs, guarantees or endorses this Note, to the extent allowed by law, waive
presentment, demand for payment, protest and notice of dishonor. Upon any change
in the terms of this Note, and unless otherwise expressly stated in writing, no
party who signs this Note, whether as maker, guarantor, accommodation maker or
endorser, shall be released from liability. All such parties agree that Lender
may renew or extend (repeatedly and for any length of time) this loan, or
release any party or guarantor or collateral; or impair, fail to realize upon or
perfect Lender's security Interest in the collateral; and take any other action
deemed necessary by Lender without the consent of or notice to anyone. All such
parties also agree that Lender may modify this loan without the consent of or
notice to anyone other than the party with whom the modification is made.

PRIOR TO SIGNING THIS NOTE, BORROWER READ AND UNDERSTOOD ALL THE PROVISIONS OF
THIS NOTE, INCLUDING THE VARIABLE INTEREST RATE PROVISIONS. BORROWER AGREES TO
THE TERMS OF THE NOTE AND ACKNOWLEDGES RECEIPT OF A COMPLETED COPY OF THE NOTE.

BORROWER:

INFORMEDIX, INC.

By:/s/ Bruce Kehr
   -----------------------------------------
    Bruce A. Kehr, CEO

===============================================================================
Variable Rate. Irregular LASER PRO, Reg. U.S. Pat. & T.M. Off., Ver. 3.26c(c)
2001 CFI ProServices, Inc. All rights reserved. [VA-D20 F3.26b INFORM.LN]

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