Nyko's Wand debuted last year at CES, and this year they have something to answer the question of why people need a Wiimote AND a Wii Motion Plus separately. It's called the Wand+.
The Wand+ doesn't have, explicitly, the exact technology found in the Wii Motion Plus—probably because they'd get sued. But it does have "Full Motion Technology" built right into the thing, and tracks 1:1 movement and is compatible with any game that takes the Wii Motion Plus accessory. And instead of having to buy a separate device, the whole thing is in one package for just $40.
Nyko's solution also continues their other bit of technology introduced in the original Wand, which is called Trans-Port and lets them hook up additional accessories to the Wand and passes sound and vibration signals to them. The Wand+ should launch in March 2010.