Don't you hate Speed Traps?
I recently received a speeding ticket in the mail that included a photo of my car taken by a traffic camera. What bothered me most was that I'm one of the slowest drivers you will ever see on the road. I make it a point to always go no faster than the speed limit, but in this particular case, I wasn't aware that the speed limit in that particular area was lower than normal. It was a classic speed trap.
If I knew about the lower speed in that area, I definitely would've slowed down, and avoided the ticket. That's when I thought about the idea of an App that runs in the background on your iPhone that could tell you when you are driving over the speed limit. If such an App existed, it could've warned me before I approached the speed trap.