title: Creating Turn-Turn Navigation iPhone app
body: <p>I am trying to build a turn-by-turn navigation app like TomTom or Mapquest, and I am looking for some help in getting started, in the direction of available options and licensing (if any). </p>
  
  <p>Technically, I think its fairly easy to plot the current location or address on map via Core Location. But I have some question more specific to routing.<br>
  - Is there a Google/or any other API for turn-by-turn directions?<br>
  - Technically, what is the best way to go about creating an app like that using available 3rd party/open source tools (maps, routes, POI, etc.)?<br>
  - What are the potential challenges or do's and dont's?</p>