iPhone/iPod touch only: Free iPhone application Dual Level uses your iPhone or iPod touch's accelerometer to turn your device into a dual-bubble level. That's really all it does, and though it's a bit jumpy at times, it seems to work pretty well. You probably shouldn't trust this level with building your home, but for a quick and crude leveling job, it seems like it could come in handy (hopefully it'll only improve with updates). This is one app that probably works best with iPod touches and first generation iPhones, since the iPhone 3G's curved back doesn't really help with leveling. Dual Level is a free download from the iTunes store.