The one problem with that solution, and any of these scenarios is just one thing, albeit a probably rare to never happen occurrence. That is the scenario where your car (with built in GPS) or phone is stolen or otherwise in the hands of someone unauthorized and they have your address. In this case if someone has your phone and they approach your house, you just let them in the garage. That's maybe not quite as bad as actually disarming the system at the same time but it at least gives them access to the stuff in the garage.
IMHO, security is more important than coolness and while all these ideas are cool they are simply not secure. I think one of the safest methods of coming home to enter your garage is as bsr mentioned - the Flash2Pass. The reason for that is security by obscurity. Even if someone has your car they will likely have no clue how to open the garage. the other method may be a wireless keyfob where you have to press a few buttons in a certain order or something.
Believe me, I am not trying to take anything away from these innovative and cool ideas and thought processes, just that I think they are not secure enough. Of course the chances of theft may be very small and worth the risk to you so by all means these are all good and viable options as long as you understand the risks.
