simple transmitter reciver circuit wanted

hi all
i'm looking for a simple transmitter and receiver circuit 9 volt
it's for a humane mouse trap when the trap door closes i want a signal sending to a simple receiver so i can tell that the trap has gone off its around 20 meters away.
if not i would like a simple transmitter circuit so a signal is sent to my fm radio
all the circuits i can find on the net use an electret mic i just want a simple tone
any help would be appreciated with links

hi if you are interested buy a toy rc car for 10-15$ and disasembly the circuit board of the transmiter and conect two wires in one of the swiches

As jurgen said, consider buying a commercial product the already performs that function. e.g. a wireless doorbell fits the bill