A $10 beeper beacon made from an FM wireless microphone can be fun project. Especially for on-foot fox hunts in local parks and the like. Hounds don't need special equipment - just an FM broadcast receiver can tune the fox in.
This video hunts down a hidden 88 MHz beacon transmitter and gives some techniques for finding its direction even if you lack a directional antenna. It then describes the circuit which is basically an FM wireless microphone with audio beeper pulsated by a flashing LED. https://www.youtube.com/watch?v=NCbOMyz5z7E