Isn't that Metroid Pinball, not Prime?
Yes, the picture in the article linked is for Pinball, but the article itself talks about Prime. Confusing, no?
Technically there's already a rumble pack out there for the DS - the Wario Twisted pack, which in addition to a gyro also contains rumble functionality (and works great in the DS). Why not just modify those and give us that awesome gyro functionality while they're at it?