Android (rooted): The PS3's controller is great for games, but it makes text entry a pain in the nethers and it's too big to fit in your pocket. Sure you don't put it down while gaming, but when watching videos on YouTube, it always seems to end up out of reach. Luckily for us, Android app BlueputDroid solves these problems.
BlueputDroid connects to your PS3 or PC via Bluetooth. Once the devices are paired, you can use the app to control your system, using it to mimic a keyboard or a six-axis controller. The lack of physical buttons makes it impossible to use your phone without looking at it so it's pretty useless for gaming, but it is more than adequate for most other tasks you'll want to perform on the system.
The keyboard makes messaging PSN friends, searching on YouTube or entering account information easier than ever. And it's great for controlling your computer from afar, but it's far from the only app that can do so.
Hit the link below to try it out. Not all phones are compatible with this app; if you experience an error the developer suggests you try running on a different ROM.
BlueputDroid [Google Play]