^with those bluetooth GPS receiver, if you trying to use them in or near high rise buildings, it's very hard to connect to the satellites! (happened to me, switched the GPS receiver off, then turning it on after 30mins later, couldn't connect...but once we were outside CBD we were connected. but the only major difference between a mobile phone GPS n a Portable GPS System, the Portable GPS System has better/stronger satellites receiver. What i mean by this is that, if you're inside your house, with the bluetooth GPS receiver you won't be able to connect, while the Portable GPS might give you 1-2 satellites and yet it still can calculate your route.