It appears that the default Bluetooth GUI wasn't designed with gamepads in mind. You can still get your OUYA gamepad working, though. You should be able to use the default Bluetooth GUI (see the other answer) - if for some reason you can't this fallback method also works (with some caveats).
Pre-install
Before you start, install bluez-compat (to make the connection with hidd) and joystick-gtk (to test the gamepad) as follows:
sudo apt install bluez-compat jstest-gtk
Scan and connect
Now press hold down the OUYA button on the controller to make it discoverable. It should start by flashing all four lights, then flash only two lights. Once it is doing this, enter the following command to scan for it:
hcitool scan
It should appear as "OUYA gamepad" with a long address after it. You can now connect to it with:
sudo hidd --connect <ADDRESS>
(replace with the address from the scan).
Confirm it works
You should immediately be able to move the mouse pointer with the OUYA gamepad touchpad. Additionally, a wireless mouse indicator should appear next to the Bluetooth adapter icon.
Finally, you can confirm that gamepad input is working by running jstest-gtk from the Dash.
Drawbacks with this approach
bluez-compat is self-described as being a legacy package. "These binaries are not supported, and will go away again in the future." It would be ideal to use a more modern package.
- Because we use
sudo to connect, a lock icon appears on the Bluetooth indicator. (Does this have any effect?)
- The gamepad is not permanently added to the list of Bluetooth devices, and is autodiscoverable (e.g. next time you reboot, you can't just make the controller discoverable again, you have to repeat the scan and connect process).
- Using the default Bluetooth GUI does not have any of these drawbacks.