tehsage is right. It's your setup. Most likely your room lighting. You will probably find it plays perfectly in the dark.
Then it is just a matter of checking where the problem is. For me it was a halogen uplighter at the back of the room reflecting off a corner of a mirror frame (it is that sensitive). Then just move stuff around until you don't have the problem any more.
As to what WM+ does:
The Wiimote uses accelerometers, which detect acceleration. So they can tell when you're moving and they can tell which way is down (acceleration due to gravity).
WM+ keeps that, and adds gyroscopes which - once calibrated - will detect orientation in all three directions. So it will know which direction it is pointing as well as which way up it is.
So, expect WM+ games to require fairly frequent pointing-at-the-screen (to keep the calibration accurate, but it will be well-disguised in the gameplay) and 1-1 directional matching. Like swords for example.
It still won't know physical position in space. So don't expect a Wii Music where you can play the high notes to your right and the low ones to your left.







