Just whistle

 Local Blog Jmt Stuff Tag-For-RemoteFound in the Osamanoidea shop in Shinkuku, Tokyo, this is an object-finder with a whistle interface . The yellow tag can be attached to your TV remote or keychain. Then if you lose the object, you blow into the black whistle. The tag responds with a sound and a flashing LED. Link

UPDATE: Several readers point out that Radio Shack sells a similar device. Of course, the packaging can't compete though. Link