The following are the GPS apps that I have successful used now for some time.....
1- Tom Tom.....we use this as our "Turn by Turn" Navigation app for car and bike and even walking within a city centre. App uses AGPS and doesn't rely on 3G coverage..... The Tom Tom app is one of the more expensive apple Navigation apps at $69, but we use it like this....we have a iPhone each, a 3G iPad, and a daughter now driving with a iPhone.....all of the devices share the Tom Tom app.....updated regularly, usable POI, share location function via txt(data coverage needed) iPhones mount in cradle on Cars and bike. So as we have no need to buy and replace a GPS device now $69 ONCE off works out cheap to run 4 devices.
2- GPS Utility....$3.95....use this app as for 4WD applications and at Search & Rescue work, the app gives the ability to show your GPS locations in a number of mediums..... various Long/Lats, UTM, MGRS and convert between them. This is great for using it from a topographical ground based mapping and converting to Long/Lats for helicopter references and back, also has google earth mapping (data coverage required for this function only).
3- Mud Map HD (old VMS) and Mud Map2 (new version of Mud MapHD)......this app I use for my other hobby of 4WDing/Camping/hiking and SAR work. This app has a number of off-road maps for all over Australia with detailed maps on the more popular 4x4 destinations in variuos scales from 1:250K down to 1:50K i.e Gibb River Rd, Cape York, Flinders ranges, Simpson desert. The app also allows you to down load the 1:25K (lots of detail) Topoveiw maps for the particular area your travelling. POI's, plotting, bread crumbing, geocaching,
etc.
Chris