Android App using GPS

I am looking to get a quote on getting an app developed for Android. Here are some details of the project. If you check out this website / app [login to view URL], you will get a good idea of what I'm looking for. My concept is a bit different, but works on the same principle. As the user drives past a specific point, a picture would display on the screen and an audio message is played. There would be a map displayed on the phone with the points and the vehicles position. Another important point is that it doesn't rely on a data connection, so the user can download the "tour" (mine won’t be a tour, but you get the point) ahead of time using WIFI. Some other things I am looking for... - I will be continually adding / updating Points of Interest as well as adding different areas (similar to the different 'tours' GYPSY Guide offers), so I need a back end developed so that I can add new points and upload the picture / audio file on my own. I'm essentially looking for someone to produce and design the main app, but give me the ability to add or edit the content, as it will be growing and changing quite a bit and wouldn't be economical to pay a developer for every change (aside from bigger app updates). All I would really need is the ability to add a point (via map or lat/long), choose an icon (there will be different icons for different points), title, picture and way to upload the audio file. - users need to be able to purchase not only the main app, but additional areas as well (just like the GYPSY Guide does). For example someone driving across the country can purchase Saskatchewan, then purchase Manitoba if they want. - I'm not sure if GYPSY Guide does this but if the user is listening to music, I'd like the app to be able to pause the music, play the audio, then have the music start again after - also if there is a way to allow the user to connect it to the car via both aux cable and Bluetooth that would be great too