iOS (Jailbroken): LockGestures makes your iDevice's home screen significantly more functional. Instead of just being able to slide to unlock, you can unlock with new gestures or use those same gestures to open apps, cycle through music, and more.
For example, if you wanted to open Safari directly from your lock screen you could tap twice with two fingers. You'd just need to assign it as the launch-able application and then select which gesture you want to use to open it. It's very simple, lives in Settings.app, and doesn't cost you anything to install. See the video above for a demonstration.
To get a copy of LockGestures, you'll need to jailbreak your device and search for it in Cydia. From there you can just install it like any other app and you'll be good to go.