I honestly do not know why it took soooo long for this to happen.  The last time someone tried something like this they closed shop in 2009 so I ended up with a very expensive brick (Dash Express Two-Way Internet-Connected Portable GPS Navigator).  I loved that device, but the monthly fees probably killed it among other things.  Too bad, it had the best traffic updates ever - real live traffic updates.

Magellan - SmartGPS 5" GPS with Built-In Bluetooth and Lifetime Map and Traffic Updates