Need to build a LBS app. only need a venue list from Foursquare around certain location. (e.g. my location or any point your selects)
Main view is MKMapView, that has one button. Once pressed second view, which is table view, comes in using navigation controller. each cell contains the name of each venue. DetailView from the tableView contains latitude / longitude, name and all the other information that can be retrieved.
Basically you don't have to concern OAuth since the app is not dealing with anything but the venue list. I give coordinates and the app gives that list in return.
extremely simple. innit.
Skill to use Foursquare API and objective-c for iPhone is absolutely needed.