Transmitter: 

4.5-5V supply must be thrown towards the ATtiny. The RF transmitter works best with 12V, but 4.5V proved to be enough for 35m distance (even with the receiver inside the house).

The LED is just for an indication that the button press was registered, and you can add a push button (or voice control if you like) to bring the ATtiny out of sleep mode. If you can't wire up a button to a uC without instructions, PLEASE DON'T GO AHEAD

Receiver:

This end is connected to mains voltage (240VAC for me). Ignore the photos as that was done on old board with other projects, and still used ATmega's. Line up a 7805 or your favourite regulator and feed the uC and RF module. Grab a data line from the module to a pin of your choice.

Remember to use a transistor and diode to switch the relay, don't do it directly.

I have added a push button on pin 2 as an override switch so you can still light up the back yard from inside the house while the remote is in the car.

Mains voltage alert:

Now it's time to connect your mains voltage. In my case I wired the relay in series with the normal switch, so the switch needs to stay on. In retrospect, parallel would have worked much better, but in my case it would have made the wiring difficult.

All that is remaining is to upload the firmware, insert batteries, and enjoy remote lights at home. Receiver Arduino code: http://hastebin.com/rosumaneri.coffee

Transmitter Arduino code: http://hastebin.com/xalonaceqe.coffee

One last thing, this system is vulnerable to a replay attack. I was aware of it since I started, but decided not to bother with a rolling code system as this does not open doors or anything.

If you do try this however and end up with a nice PCB and case for the transmitter and/or receiver, gimme a shout, I'd like to see pics! I'm dismanteling mine now for a house move. For the new house I will buy a kit from dx, but this was a fun learning experience!

DO NOT TRY THIS AT HOME!

Okay, with that out of the way, when you do try this, don't do it like me!