the "silver box" you guys are describing sounds a lot to me like a "carputer". (car computer...like your home computer but in a car for those of you that don't get the terminology)
lots of people are doing things like this - putting 7" touchscreens in their car and hiding an actual computer inside their dash cobbled together from parts bought at the computer store and power supplies obtained on mp3car.com (sorry for the plug) and having their radio / everything else controllable via the computer.
INCLUDING a few plug-ins that ive seen to control HVAC using the same comptuer. (with a few wiring changes and a USB/Serial connector)
just so you all know...if gm did this it could launch a new industry in the computer world lol...
-- edit --
i know a guy that put this kinda setup in his ion redline. he could control all his stuff, from radio to cd/dvd player - volume control, GPS - wireless internet built in...he even had the HVAC controls and software that would show him his guage readouts (Coolant temp, speed, tach, mileage, trip, fuel econ, etc) on the 7" touchscreen he put in. created a custom fiberglass bezel for it even. looked slick. cant wait for him to help me put my carputer in
