Product review (5 stars): Did what I needed it to do!  It really works.  Follow the simple instructions.
I recently had purchased an new Whirlpool High Efficiency washer and dryer.  The washer would wash the clothes and the dryer would dry the clothes just fine.  However, at random times the dryer would alarm for some unknown reason.  I had called my local dealer/installer and also stopped by his business and explained the alarm.  He didn't have any idea.  I really don't know if it was really an "alarm" or not since the control panel didn't show any alarm.  Whenever the alarm sounded (continuously a 1-2 second beep until the dryer was turned off or the door was opened for a few seconds and then closed again) I, or my wife, would go to the dryer and check it out by opening the door and checking the lint filter and insuring that the lint filter was not covered in lint (which it wasn't - we always ensured that the lint filter was clear of any remaining lint from the previous drying cycle).  Then closed the dryer door and it may or may not run a full drying cycle until the next random alarm sounded.
I was searching on the Internet and stumbled across this item and thought that this may solve my problem.  It was relatively cheap ($25.45) and would not hurt to try.  My house is only 6 years old, so I wasn't sure that lint trapped in the exhaust pipe could be that bad.  While I was waiting on the item to arrive I decided to inspect the exhaust pipe from outside the house by shining a flash light inside.  However, I could not tell for sure that any of the pipe was clogged or obstructed.  My dryer exhaust pipe is made of thin wall 6" PVC which leaves the wall in the laundry room and immediately enters a 90* turn downward the approximately 1-2' then to another 90* turn, then a straight run approximately 15 feet to the outside of the house.  HOWEVER, when the item arrived I proceeded to perform a cleaning.  First, I started from the outside with the dryer on air/fluff.  I could not believe the amount of lint that this system cleaned out (WARNING:  YOU SHOULD USE A FILTER MASK WHILE USING THIS ITEM).  Just cleaning from the outside to the inside as far as it could reach I was able to accumulate enough lint to fill a plastic grocery bag.  I then proceeded to clean from the inside out and another half plastic bag full came out.  WOW!  It's now been approximately two weeks since the cleaning and the dryer has not sounded a warning beep.  Yes, I would definitely recommend this product to keep around the house for use on a regular basis.  I am planning on using this at least twice a year from now on.  Thank you for taking the time to read my review.