Anyone have an idea on how to get a handle on detailed sales information for the Nintendo Motion Plus?

the sales of Wii Sports Resort and other bundled sales combined can give you an idea, as for the loner packs... I dont know

Every now and then, Nintendo will throw out some information in a press release. That's about it.

IIRC, WM+ install base is about twice the size of Wii Sports Resort's sales.

Twice the size makes sense because you really need at least two WM+ for WSR

It was when they gave some info, but it may not track like that (considering WSR wasn't the first game with WM+).

Who knows though, as other games like RS2 will be bundled with it.

Somewhere b/t 10-15 million.

Here's the press release I was talking about:

http://www.nintendo.com/whatsnew/detail/AZ0OEYjv_m0VrVAke1-qbmNDv71evaNg

"Through the end of August, Wii Sports Resort has already sold more than 1.25 million units in the United States alone, according to the NPD Group. Nearly 2.9 million Wii MotionPlus accessories are in the hands of the public. That includes all those sold with Wii Sports Resort, standalone sales of 1.36 million and an additional 257,000 bundled with Tiger Woods PGA TOUR 10. "

As Demotruk says, we can't be sure that the 2:1 ratio will persist, but more and more WM+ bundles keep popping up. There's the NHL2K10 bundle and a new WSR bundle with two WM+ dongles. Take the 2:1 ratio as a guideline rather than gospel.

Also, this release only pertains to the US region. Other regions might be more or less keen to buy additional WM+ dongles.

I would say about 8m right now!

8M? No way. WSR alone is at 7M.

Don't forget that some of the WSR copies come with two Wii Motion Plus add ons.