Nearly useless, but funny. It's easy to perform. You need:
-PS3
-HDMI-cable
-Wii U GamePad
-HDTV, which is
CEC-compatible
All you have to do, is to activate CEC on your TV (it's manual should explain how to do that) and your PS3 and connect both with the HDMI-cable. Configure the remote-control-function of the Wii U GamePad that you can use it instead of your standard TV-remote.
Now, when your PS3 is on and and displayed on the screen and you activate the remote function of the GamePad with the "TV"-button, the D-pad works like the arrowkeys, "A" like "Enter" or "OK" and "B" like "Back" or "Exit" on your TV-remote. Thanks to CEC, your TV will send this input via HDMI to the PlayStation, so your GamePad-D-pad works like the D-pad of the PS3-controller, "A" like "X" and "B" like the "O"-button. In my case, I can also boot the PS3 with CEC. Too bad, that the Sony-console needs a PS3-pad for gameplay... but listen to music or watching photos or videos works without any problems.