Again, this is the first time I'd seen it during my current stay at the Seattle Sheraton. There is a hang-card in the room that you simply put on your door prior to 2:00 am and the next morning there is a $5 restaurant gift card slid under your door. You either use that gift card or go to the front desk and exchange it for 500 Starpoints. Very simple; no signup necessary. Not sure if other Sheratons or Starwood hotels are doing it.