While most of the apps making use of the iPhone 4's gyroscope have centered around augmented reality, here's one doing something different. Gyro Air Drums is an app that supposedly lets you use your iPhone as a "virtual drumstick," waving and tapping it on a virtual drum. You can move your iPhone in a 300 degree rotation in real life, hitting various drums on upper or lower levels. And when you move the iPhone, your screen will rotate along with the movement, viewing all of the various instruments, from the snare and hi-hat to more fun things like a cowbell or a taiko drum.
As you can see above, it's only one drum hit at a time, but presumably if you have two iPhone 4s, or a quick and accurate wrist, you'll be able to play a full drum beat. But at least it's a cool idea -- I was hoping we'd see more inventive uses of the gyroscope like this. The app is US$2.99 on the App Store right now, or there's a free lite version with a limited number of drums if you just want to play around.