I put these in my S2000, and was planning on putting them in my Nismo as well under the factory seats.
Then I realized how quickly that little cabin warms up. Even when it's around 30-40deg out.
If I do decide to install. I will photograph and step by step it. It's really easy. You run power to the seats of aux, on a fuse. Switches in the center console, etc.
Take out the seats, peel back the covers and apply the heat pads. once in place and cut to fit, you reapply the covers.
I had mine done on the s2000 in about 3 hours. No fuss no muss....
Local uphulstery shops will do these as well.
OEM Type Universal Carbon Fiber Heated Seat Heater Kit - eBay (item 320624629318 end time Feb-28-11 09:15:49 PST)