You might have seen how I modded a transmitter I got from E-bay and installed it in my overhead console:
I got two more from E-bay and modded those as well with 12V hookup, 1 red LED, and 3 switches. I hardwired in all new parts and sealed them for durability.
If you wish to install these yourself you need only hook up the 12v power to a vehicle source (over head light in my case), and drill 4 holes (3 for switches and one for LED mount. Of course you can put these in any car, anywhere you wish to install them. I just like the overhead sunglass holder since it's hidden when not in use (and who uses the sunglass holder anyway??).
I'll offer IT up to the first one who PMs me. I figure with cost, parts, some of my time, and shipping I'll let IT go for $60.
#1 (in original case) - sold!
#2 (in a custom case)