LOL at the iPhone..
I just think the average phone or small tablet.. Is too much of a compromise for a GPS unit which is important enough to want a dedicated, ruggedized device. Sure they can 'make do' and are very useful with a data connection for route planning, to double check, or as a very rough guide.. But when it comes to ongoing routing you want something made for the task and as much as it pains me, due to how awful the software and customer support can be Garmin just make solid hardware. I keep one in each car, and one for all my bikes.
In fact after not liking the original zumo that much, the one Keld recently purchased seems a great device. Might get one of those just for my road bike setup. The screen sure beats out the tougher 60csx I havent upgraded.