Unfortunately for Dash, they are killing their GPS devices. Does that mean it was a bad idea? Not at all. It’s a GREAT idea.
Now, would this make a great iPhone app? Probably, but the problem with it is that if you’re giving routing information, you need to know where you’re going in the first place? Why not let the iPhone’s built-in map do it? Well, that’s against the iPhone rules.
Someone’s going to figure out how to do this properly, either through an agreement with Apple, after Apple loosens the rules up, or through a Dash-like device that does this in a way the company can keep going. (Maybe Garmin will buy Dash out?)