HEYU is a text-based console program for remotely controlling lights and appliances in the home or office. It is made available under a free and open source license.

Heyu uses the CM11A computer interface to send and receive X10 control signals over the AC power lines to modules which can turn On, Off, or Dim attached lamps or appliances. It can store a schedule of timed events in the CM11A memory for execution when the computer is turned off or disconnected.

Heyu supports an optional W800RF32A, MR26A, or RFXCOM RF receiver connected to a second port as an auxiliary input device for X10 RF signals.

Heyu can also use an optional CM17A interface to transmit X10 RF signals.