Hi,
It depends on the distance you wanna reach and the data rate.
For short range and low data rate, you can use one uC output pint to command a transistor that turns on and off an oscillaotr at, say, 27MHz. That is, data is sent using OOK. It's up to you to implement the communication protocol.
Some "wireless" mice use this principle (logitech for instance).
There are also some low cost transmitters (see Micrel) and you have to look for the matching receiver.
Good luck
Humungus