<PAGE>

                                                                   EXHIBIT 10.50

                        AMENDED AND RESTATED STOCK OPTION

         THIS CERTIFIES THAT, FOR VALUE RECEIVED, Invisa, Inc., a Nevada
corporation ("Invisa, Inc." or the "Company") has, on November 8, 2002, granted
to G.M. Capital Partners Ltd. ("Holder") the right and option until December 31,
2005 to purchase 500,000 shares of Common Stock of Invisa, Inc., at a purchase
price of $3.50 per share.

         The Company commits that it will, on one occasion during the term of
this Option, cause the shares covered by this Option to be registered under the
Securities Act of 1933 (the "Act"), in accordance with the following: (i) the
cost of any such Registration Statement shall be borne solely by the Company
provided that the Company shall not be required to pay any commissions, legal
fees or other sales cost incurred by the Holder; (ii) commencing on January 1,
2004, Holder shall have the right to demand that the Company file and exercise
reasonable efforts to effect a Registration Statement under the Act covering
250,000 shares which may be purchased under this Option unless 250,000 shares
which may be purchased under this Option have previously been registered under
the Act by the Company; and (iii) commencing on July 1, 2005, Holder shall have
the additional right to demand that the Company file and exercise reasonable
efforts to effect a Registration Statement under the Act covering the remaining
250,000 shares which may be purchased under this Option unless the Company has
previously registered all 500,000 shares which may be purchased under this
Option. Such demand to register under subparagraph (ii) and under subparagraph
(iii) shall be in writing, executed by G.M. Capital Partners Ltd. and shall
state Holder's intention to exercise the Option to purchase the shares demanded
to be registered.

         In the event of a stock dividend or stock split resulting in the number
of outstanding of shares of the Company being changed, the applicable exercise
price and number of shares, as provided in this Option, shall be proportionately
adjusted. In the event of the merger, consolidation, or combination of the
Company into another company or entity which survives that transaction, the
shares which may be purchased under this Option shall be converted into an
equivalent number of shares of the surviving entity. In the event of the sale of
all or substantially all of the assets of the Company, the shares which may be
purchased upon the exercise of the Option shall be treated in any distribution
as if said shares are issued and outstanding, with the exception that the
exercise price under this Option shall be deducted from the amount to be
distributed on a per-share basis.

<PAGE>

                                                                               2


         The grant of this Option is made without registration under the Act by
reason of a specific exemption. The Option and shares to be issued at exercise
shall (unless registered in accordance with this Option) be restricted as to
transfer in accordance with Rule 144 of the Act.

         As a condition to the issuance of shares of Common Stock of the Company
under this Option, the Holder agrees to remit to the Company at the time of any
exercise of this Option any taxes required to be withheld by the Company under
Federal, State, or Local law as a result of the exercise of this Option.

         This Option may not be transferred without the consent of the Company.

         The Holder shall not have any of the rights of a shareholder with
respect to any shares of the Company's common stock until the purchase price for
the shares has been paid to the Company.

         THIS AMENDED AND RESTATED OPTION AGREEMENT AMENDS AND RESTATES THE
OPTION AGREEMENT BETWEEN THE COMPANY AND THE HOLDER FOR THE MAY 7, 2002 GRANT OF
THE RIGHT AND OPTION UNTIL JUNE 30, 2004 TO PURCHASE 500,000 SHARES OF THE
COMPANY'S COMMON STOCK AT A PURCHASE PRICE OF $5.50 PER SHARE (THE "MAY 7, 2002
OPTION"). THIS AMENDED AND RESTATED OPTION SUPERSEDES AND REPLACES, IN ITS
ENTIRETY, THE MAY 7, 2002 OPTION WHICH THE COMPANY AND THE HOLDER HEREBY
ACKNOWLEDGE AND AGREE IS CANCELLED BY THE PARTIES' EXECUTION OF THIS AMENDED AND
RESTATED OPTION, AND THE HOLDER ACKNOWLEDGES THAT THE MAY 7, 2002 OPTION WILL BE
SHOWN AS CANCELLED ON THE BOOKS AND RECORDS OF THE COMPANY AND REPLACED WITH
THIS AMENDED AND RESTATED OPTION. THE HOLDER FURTHER AGREES THAT IT WILL RETURN
THE MAY 7, 2002 OPTION TO THE COMPANY MARKED CANCELLED.

         The Company has caused this Amended and Restated Option Agreement to be
executed in the name of the Company by its corporate officer having been duly
authorized, and the Holder has hereunto set Holder's hand and seal as of the
date and year first above written.



INVISA, INC.                              AGREED TO AND ACCEPTED BY HOLDER:
a Nevada corporation                      G.M. CAPITAL PARTNERS, LTD.



By: /s/ Stephen A. Michael, President     By:         /s/ J. A. Michie
   ----------------------------------        -----------------------------------
Its: President                            Its:       Managing Director