Wiring was a bugger, because I wanted it connected up to the fusebox to look like stock. I added two relays (one for each seat) and ran wires under the carpet to each seat. I had to buy a connector for the switch from Toyota, that cost a fair bit as I had to buy the terminals which were something like £3-4 each.
You can just bodge it by soldering to the switch direct but I didn't want to.
There is a circuit diagram on here- http://mkivsupra.net/vbb/showthread.php?4811-Heated-Front-Seats&p=52213&viewfull=1#post52213
The way i did it was from the switch, wires go to the two relays, I conveniently mounted these on a screw on the heater channel behind the stereo on the left. Then wires from the relay go to the fusebox under drivers kick panel and also to the seats under the carpet.
Hope thats any help to you, Photos would have been a good idea but didn't think of it at the time.