Here's another iPhone application that demonstrates that soon there is nothing you won't be able to know if you have just one device. DevToaster has created an app called Rev that reads information straight from the OBD-II port on your car and displays it on your iPhone. When it's fully operational, Rev can display things like vehicle speed, RPM, fuel consumption, calculated engine load, and a host of other parameters. You'll even be able to check and reset engine and error codes.

We've known for a while that the new iPhone 3G would have the magic of GPS, but we didn't fully realize how that power might benefit car owners. While we've seen a few semi-cool, car-centric applications available for the device -- from mpg calculators to maintenance reminders -- this program could prove the most useful for the forgetful among us.

After parking your car at a crowded shopping mall, users of G-Park tell their iPhone where their car is. When they wrap up their shopping, the application will provide directions back to the car.