Wireless control of immersion heater?

I have one - I bawl "Whoever's turned that bloody immersion on again, switch it off!"

Doesn't work too well though (and so I fitted a 'booster' switch - ie

David

Wireless control switches are sold for heating controls. However they generally won't have 13A contact(s) so you'll probably need a contactor unit to switch the actually heater.

The simplest way for the computer to control the wireless sender is to use the a pin on the (probably unused) parallel port to drive a 5V relay. [Or you might be able to do something with the probably unused 9pin serial port at 12V]

Others will probably tell you how easy it is to fix up a tele-thermometer with off the shelf bits.

However over-arching all this is the fact that with a well insulated modern HW cylinder the standing loss will be less than 100W and the built-in thermostat on the heater can be left to control the HW temp. A simple (high-current) time switch can reduce the standing losses a bit provided your lifestyle is not totally random.

HTH