Small Radio-Activated Alarm / Key Finder

Hi Guys,

I'm quite new to electronics (I'm a programmer by trade), but I'm a quick learner.

I want to make a sort of radio Key-Finder (similar to something like this), but I'd like the "receiver" end to be rather small in size.  I'm trying to figure out how to go about starting something like this, but I would really appreciate some direction.

Some questions:

1.)  Are there products that I can take apart and re-purpose for this?
2.)  Could something like this, for example, be a starting point for the radio "receiver" end?
3.)  I imagine that I would need at least a small battery (flat watch battery?), perhaps a small flat Piezeio-Electric buzzer (like one of these?) and the radio receiver.
4.)  Is this a project that needs something like an Arduino board to handle any logic?
5.)  Can I re-purpose a car alarm remote for the "remote" piece?

Thanks for any thoughts and direction.


The product you linked to has the receiver end about as small as it gets. The largest thing in it is the buzzer and battery. But you can certainly purchase that item and then see what you can do to make it smaller.