Not that I'm adding to the conversatin but I too have read of both of those innovations, BMW's throttleless system and Saab's variable compression.
The BMW thing basically varies the lift and timing on the valves to such a degree that it keeps the engine at the best volumetric efficiency for the given load and speed. They barely crack open at low speeds but really get wide when needed.
Saab's thing has the cylinders and crank seperatated, and a pivoting device that makes the pistons ride higher or lower in the cylinders to vary the compression. They, Saab, also were playing with a variable spark gap engine where the piston has a little "titty" in the center that acts like the ground electrode on the spark plug. I'm not sure what the reasoning behind that one was though.