Yeah, I haven't seen that exact method though. The method I've seen is very common for big offroading/mud tires, usually only over 35" though. People with big offroading tires that are almost impossible to balance will pour a few thousand (something like that) airsoft pellets into the tire. Under 35mph they just kinda roll around and don't do anything, but above that, they distribute around the tire to balance it better than wheel weights could do.
I wouldn't use it in my bmw, unless these ones that you point out work better than the method I have seen for Jeeps/other 4x4s.
edit: The reason I wouldn't use it, is that it still looks like that you need to have some speed before the media will be able to find the right spot, as with the pellets I've seen. But maybe a slightly off-balance tire at 30mph doesn't matter when it's perfect at higher speeds?...that would make sense I guess