I tried Marco Polo around the house, first putting the phone on a dresser. That was an easy one -- I said "Marco" and the phone replied. I also put the iPhone under a couple of blankets, and that worked too. Then I put my iPhone in a drawer in the kitchen, and while the sound was muffled, I could hear it respond. Obviously, if I got too far away -- like two rooms away -- it wouldn't trigger. But I would be quite happy to shout out a couple of different "Marco's" to find my lost phone.