I have the Energie exerciser and voted for it.
The glass choices aren't going to give you the weight and resistance that the Energie and Kegelcisor, both made of metal, will. energie is cheaper because it isn't solid steel - it's a metal composite coated in safe plastic. It does the trick MUCH more effectively than kegel balls, which are mainly just fun.
My second choice would be the Kegelcisor for much the same reasons. Both come with instructions. I just feel that energie is pretty tough to beat unless you need something pretty and stainless steel.