I am using my WII with a projector. The Wii sits behind me, plugged into my AV receiver and the screen is 7 metres away. You can buy a wireless motion bar quite cheaply from Amazon/Ebay etc. Mine requires 6 AA batteries but lasts for ages. The motion bar only has two infra red LED's (invisible to the eye) and the remote 'sees' them - the motion bar does NOTHING else. Amazingly you can get the wii to work perfectly with 2 candles placed strategically in place of the motion bar!!
My motion bar sits on a small table about 3 metres in front of the projector (but is only moved there when playing the Wii).
In reality the motion bar is not needed for all games and mostly is only vital for the intial menu. Once in many games such as 'Mario Kart', 'Wii Sports', 'Mario Galaxy' etc you can switch it off reducing the battery usage massively.
Most of the motion sensing is done within the wiimote and most menus can be navigated in game with the wiimote buttons.