We've mentioned Trapster once here on the site before, but we haven't really covered it in any depth yet, I believe. It's the official iPhone app [iTunes link] for an online database of speed traps, so that you can get fair warning when the police are checking speeds in a certain part of town. It's a very popular app with over 3 million users already (and if you're constantly looking to dodge speed traps, you've probably already heard of it), but as with all community databases, one of the questions is always confidence: is the information you're getting true, or is it a perception that could be wrong?
The company has just released version 4.0 out onto the App Store, and most of the upgrades are designed to help you out with confidence in their listings. There's a new feature called Patrol, which will show you just how recently another Trapster user has driven down the same road you're on, which means the information there is much more recent.
Another mode called Caravan will actually let you watch the locations of friends or other users in real-time, so if you're road-tripping with friends, you can track your trip together. There's new Facebook and iPhone connections, and lots of new "trap types," so you can even track accidents, construction zones, or just mark off dangerous intersections.
Sounds good, and even better, the app is completely free. The only issue we've heard from users so far is that the app can use battery power like crazy (given that it's tracking GPS and sending information back and forth constantly), but if you've got a car charger going while you're driving around, that shouldn't be an issue. If you do a lot of traveling with your iPhone, it's definitely worth a look.