Just a quick thought on security...
Dave, I know you've already thought about this, but it's probably worth mentioning to others.
Imagine the scenario... You get mugged and your keys are stolen. Your friendly neighborhood mugger uses your car remote to locate your vehicle and drives it away. He then uses your GPS system (or your car registration if you're low-tech) to locate where you live. On your visor is your garage door opener so he can get at least part way into your house and he knows you're not at home because he mugged you, stole your car and left you stranded at Radio Shark. Your car is equipped with your latest idea in occupancy sensing and thoughtfully disarms your home alarm for your mugger, switches all the important lights on for him and Kate tells him that your wife is not yet home.
How many toys he can load into your car in the time available to him depends on how far from home you got mugged, police response times and how big your vehicle is.
Of course, if you're using your key holder DS10A gadget then your mugger probably wouldn't know to hang the keys up when he gets home, but the idea of a vehicle opening your home completely is pretty scary. I'd rather press a few buttons than have my house emptied.
The above is actually just a scary halloween story and could never possibly happen in real life - unless you were born in London, Paris or New York in which case it's already happened to you.