http://rover.ebay.com/rover/0/e11021...=exe%2cext=ext

I use these at work
above link says $160 each.
super easy to program- graphically
requires $100 cable though

this model runs on 12VDC
so, you could make a bitchin' anti theft system.

several inputs and outputs

you could disable spark, starter, and/or fuel pump [electric] unless your favorite combination of things occurs- anything you can dream up.

Lights have been on >3seconds plus brakes on

secret switch activated plus brakes off

you could even have the car allowed to idle but not drive away.

 

Figure out how to make one of those operate a 4L80E and you'll have something. Actually, shifting is really just a function of operating one of two solenoid shift valves, plus the PWM line pressure control.