Koenigsegg camless engine and compressed air hybrid
 

You can skip the first couple of minutes, the interesting bit is toward the end.

http://www.youtube.com/watch?v=Bch5B23_pu0

Fascinating stuff!

I've been thinking about doing just this sort of thing! Too bad I didn't have all the money ):

super cool

Finally getting rid of the cam shaft. Amazing it took so long. One day. all but the cheapest engines will have computer actuated valves.

My question is this: where does the air pressure come from? Would electric actuation be more or less efficient?

From turning the engine into an air pump on deceleration. And I presume there's an ICE driven pump for air demands outside of decel...?

You are probably right, I wonder if there's any tricks to starting it up if the cars has been sitting for a while. I suppose it would have to always keep some pressure built up for the next startup, until the compressor could build up more pressure. As a supercar I would imagine that it sits parked far more often than it's driven, I wonder if there are any tricks to it like relieving pressure before storage, and building up more before startup. Although they could avoid that if it used an electrically driven air compressor that could run for a second before firing the motor.

I've once found pictures of a French 4-stroke gasser which used sleeve valves without a camshaft.

There's also Coates rotary valvetrain:
Coates International Ltd. - Home
No cams...

The Koenigsegg video is very cool and has a nice explanation on how it works. But, it's not exactly new... BMW had a functional protype (using electric solenoids IIRC) about a decade ago. Still hasn't made it to production yet.