Hi,
Have you guys seen http://www.sticknfind.com/
it's a sticker (not water proof) that you attach to anything you want, and you can track (distance only, non-directional) the item via bluetooth with your Iphone or some Android phones (Bluetooth 4.0 not standardized in Android yet).

It costs like 25 bucks each, which is not cheap.

The main applications would be to track your wallet\keys in case they get lost- and maybe even the phone itself with a secondary phone.

You can also track your luggage apparently which is neat.

This seems like a no-brainer idea and I wonder if other companies will soon enter and make this a fairly commoditized product.