Any advise for tiny electronic device that give alert sound when it is away from its host for some d

I am a very forgetful person and often lose valuable items such as wallet, PDA. It would be good to have this tiny device to paste to these items, so that when they are away from me, I can be alert ed immediately. Any web site for these kind of product ?

Any advise for tiny electronic device that give alert sound when it is away from its host for some distance ?

This is not too small but check it out:

http://www.thecyberside.com/products/par...