How can I create an item finder/sound emitter?

Question

I have a problem where property of mine is constantly taken (it's an extreme annoyance but not criminal) and I want to create a little tracking device which I can attach to things. Like a key finder, you press a button and it makes a loud noise which won't stop unless it is found.

I was wondering if anyone knew how to make these things (I intend to make a few of them for different things), how small they can get and how much it might cost to make.

It would need to emit quite a loud sound (loud enough to be heard under a pile of clothes, for example).

Much thanks.

Answer 1

This would definitely be easier to buy than to make. Sharper Image has one with 8 transceivers (you can locate 8 separate items) for $50. Here's their website:

http://www.sharperimage.com/us/en/catalog/product/sku__SI676FUN/source__25162/cm_ven__IAC_GIFTSCOM/cm_cat__feed/cm_ite__SI676FUN

They also have a device called the Loc8tor that is a tracking device with an LCD screen. That way, you can find stuff without the stuff emitting a loud sound. You just follow the direction indicated on the screen to locate the transceiver. It's more expensive, though ($169) and it only has 3 transceivers.