I'm quite new to iphone development, and been asked at work about the feasibility of an app that would involve plotting custom routes on Google maps (I can manage this though a web page), and the app itself would show users a selection of routes they can navigate using a GPS-style (turn by turn) navigation screen.
The routes would have markers that would trigger specific information, such as landmarks, etc. Again, I can have these configured through Google maps on a webpage.
The question is how would you approach this sort of app? Start from scratch or build it on any existing platform? Any tips would be appreciated, as I'm at a loss where to start.