Once in a while you discover a great little app, this is one of my most used Amateur Radio phone apps.
As I as sure you know APRS is short for Automatic Packet Reporting System, and in this case its an ideal low cost entry point. I should make clear at this point to use this you need to have a Amateur Radio Call Sign and hold a license.
In its basic form that app uses aprs.fi and wifi to transmit data packets to the APRS network and I can hear a number of my fellow Radio Hams saying its not real radio, and I respect your view.
However I also use this great little app with, my Mobilinkd http://www.mobilinkd.com/ device and my 2meter hand held, in fact when I am out and about, its normally on the side of my rucksack and I get good results, especially when on a SOTA Summit.
Do give it a try, unless of course for you its not real radio.