Most electronics appliances are controlled by IR. So you need to design a receiver to convert the RF energy into light pulses that the appliance can understand.
At the user side, you need to get someone's IC chip that has the library of appliance commands programmed into it. The chips output is a voltage pulse designed to light an IR LED. Instead of sending that pulse to an LED, you send it to an RF oscillator. The RF oscillator turns on/off the same way as the original LED does. You might want to use a crystal or saw oscillator circuit, for requency stability.