On Sun, 23 Dec 2007 10:02:45 -0800 (PST), 2apart
wrote:

Does this gaget exist?

A rftag and pocket sized transmitter set.

Put the trasmitter in you coat pocket and the rf tag in your wallet.
If the wallet is further away than, say 10 feet, the transmitter
sounds an alarm.

RFID has very limited ranges especially portable devices. 10 feet
will be too much for anything you are likely to carry around.

There is a baby monitor device that consists of a little transmitter
that goes on the kid and receiver you keep with you - when the signal
strength drops, as the kid wanders off, the alarm sounds.
--