Before there was an app store, one of the first apps created for jailbroken iPhones was a Flashlight app by the excellent Erica Sadun. It basically used the screen display as a light emitting device. We have finally come full circle with the iPhone 4 which has an actual LED for use as a flash. An enterprising developer, Michael D'Ulisse of More Blu Sky saw this as an opportunity to create a real flashlight app that projected light.
Flashlight - For iPhone 4
