These are liable to change, but for now, here is how they are mapped:

• Keypad : same as keypad on keyboard
• A : Enter (Accept, OK, next, …)
• Minus (-) : d (Delete)
• Home : escape (Exit to previous menu/exit mythfrontend)
• Plus (+) : p (Play/pause)
• 1 : Info
• 2 : Menu
• B + left : rewind to beginning of video
• B + twist wiimote : rewind (if twisted to the left) or fastforward (otherwise) with speed dependant on twist amount.
• B + A + twist wiimote: timestretching - slower (if twisted left) or faster (if twisted right)

A comment on twisting:

Point the wii remote at the screen, and twist from the elbow so that it continues to point at the screen.

The maximum fastforward/rewind speed is 180x. The speeds are dictated by mythfrontend itself. When you rotate the wiimote, you will feel a slight vibration (0.05 seconds) to let you know you have gone up or down a speed segment. To stop fastforwarding/rewinding, simply let go of B.

Beware: there is no power saving built in - however you should be able to turn the wiimote off (power button) when not in use, and turn it back on by holding down 1 and 2 to make it sync.