GM had the basic idea/solenoids in the 70's - the Cadillac 4-6-8.
The solenoid moved the fulcrum point of the rocker, not allowing the valve to open. Problem was that the computer tech. (Bendix), wasn't ready for the systems that the engineers were coming up with. Now, I know everybody will jump on the bandwagon and say that the Caddy 4-6-8 was a terrible system, the engine sucked, etc., but look what is on the market today - 30 years later - from GM and Chrysler w/ the hemi - variable displacement engines that don't open the valves. Only difference is that the companies are uncoupling the lifters internally instead of the rockers. With some modification to the hydraulic/oil system, the same basic control could be used for valve actuation.
Honda (REALLY hard for me to use the H word as a reference) used the solenoid system in F1 years ago with good results. Pit tuning w/ a lap top was done after every hot lap session. FIFA made the system illegal do the rule change, but it did work. If they could get the valvetrain to live @ 14,000 - 16,000 rpm, the manufactures will make it work @ 6,000 rpm - eventually.