My wife lost her keys, I'm hacking a key pager together. It's working . . . sorta. Answered
I was thinking: 1)An old cordless phone with a pager function I could hack apart and reuse. 2)An old cellphone for the same purpose. 3)A crystal radio learning kit. My goal is to do this for under $40--the cost of buying that way overpriced pager system you've seen advertised--and for me to learn while doing this. After reading another instructable, I was inspired to use a cheap radio controlled car.