I'd like to build (or have someone else build) a small device to
locate keys, a remote control, that sort of thing. There's a
transmitter (stationary) and a receiver (glued to whatever you're
trying to located). The receiver beeps or flashes when it's "called."
Sharper Image and Radio Shack sell devices to do this but they're $40
and up. I've seen low-cost RF microcontrollers online that supposedly
have a pretty good range. Are there any plans to build this sort of
device online?

i used a wireless rinbell for a school project once...

Was that small enough to attach to a remote control or set of keys?

What about this:
http://www.hearmore.com/store/prodView.asp?idstore=4&idproduct=5856&category=&product=Sound_Activated_Key_Finder_with_Microlight
    (unfortunately out of stock at the moment)

Or this from Sharper Image, which you may have seen, but seems to have
a better price:
http://cgi.ebay.com/Sharper-Image-RF-Locater-Pocketsize-System-NIB_W0QQitemZ9727180961QQcategoryZ73366QQrdZ1QQcmdZViewItem

Here is another one that responds to a whistle:
http://www.lifehome.com/products/412300.asp

"You can whistle, can't you?"  to quote Lauren Becall

Thanks, but that is still too large. Are there any existing plans for
a DIY key/object locator that use $1.50 microcontrollers like you can
buy from digikey.com?