Found it!

I purchased the Fitbit for my wife (her friends all use it) and she lost it in the house somewhere. She thought it was in the bedroom and we both went through the entire room twice. So I googled and found this app. Works great! It confirmed it was in the room. When I placed it on the dresser, the signal went through the roof. So we went through the drawers and found it. Great app!

wcowie about Fitbit Finder - lost Fitbit, v1.6