I just finished installing aftermarket seat heaters. I never had any previously but I bought a 2008 Ford Sport Trac for my wife which came with the OEM seat heaters. Well... after a few trips in her truck... and a couple cold mornings after shift getting in to my truck I just had to install some.
Here's the Jegs part: Warmseats #936-WSH
Here's the Jegs link: http://www.jegs.com/i/Warmseats/936/WSH/10002/-1
Although I can't post pics of the warmers themself since it looks stock (OEM leather FX2 Sport seats) I have included a couple pics of the mount location for the switches.
A couple of tips for anyone attempting this themself. If you have the electric driver's side seats, elevate the front and rear before unplugging and removing the seat. You'll need this space between the mechanical actuators to get to the upholstery clips.
Motorz.tv has a online video showing removal/disassembly of the seat skins. Here's the link: http://www.motorz.tv/blog/1104/ford-...-installation/
I used a 1/2" Forstner bit to make the holes in the dash column where the switches are mounted. I then used a small file to notch the side of the hole to align the index on the switch body. Perfect fit!
Also, find a switched power lead to connect so that when you exit the vehicle and shut it down your seat heaters don't remain on and cook your seats while draining your battery.
I have to say that having the heated seats is awesome! I work morning watch and after hauling a duty-belt around on my hips all night can really get uncomfortable. Sitting on winter cold leather seats certainly doesn't help. Now, I get in the truck and within just a couple minutes I'm good and toasty.