Geotagged event triggers
Allow the user to define an event such as playing one of your own sounds, display one of your own photos or play a music track at or near specific places. Example uses - get onto a fast stretch of road and your music changes, and changes back when you get into town again. Get a mile from a toll booth and a note appears telling you how much money to have ready. Drive near a grocer and your recording says "don't forget to get the eggs". Go past a tourist attraction and a recording tells you about it. You could even allow advertisers to pop up a note saying "turn left in half a mile for a Big Mac", (and allow users to suppress ads if they wanted to).
Stomp out AdWare commented
This could be effected via Tasker (awesome third party automation tool) and intents