Hi all,
Although this wouldn't improve your system in a big way you could also run a few other tests when deciding if the bluetooth device is your phone (for example) as you said you would check the mac address but you could also refuse to do anything if the device name doesn't match something cryptic. This would give you a huge number of combinations and would be like keeping your password on your phone. (The one problem is if anyone scans for bt devices they also get your code and your mac so don't leave your phone visible to other devices)
Hmm interesting idea though. I wouldn't like to see your carputer get a virus though
Nick