A working version of a nitro powered variable pitch quadcopter. All 4 blades are powered from a single motor, looks like it uses props/rotor assembly from regular RC helicopters.
Not only is this great if you find flying a quadcopter a little boring, but more importantly it could be a great idea behind long endurance quadcopters while we wait for battery technology to improve.
Very interesting idea 
.
After looking into this abit more it seems that he is already selling smaller electric versions (Stingray 500)
And if anyone is interested in how this works, I looked at the assembly manual and it seems the motor drives a central boom which has two belts connected at each end wich go to each of the motors.Some pics from the manual to show what I mean. Definitelymore complicated to build than a regular quadcopter, and also harder to fly.
So the blades all spin at the same speed and to change the angle the pitch on them is adjusted via the 4 servos, similar to how 3D RC helicopters 
work.
I remember reading about a 3d quad on rcgroups some time ago, there were no significant details just a low quality video and brief discussion but I wonder if that was an earlier prototype of this…
I have enough trouble flying the things right way up, even then if it moves at more than 5mph below 200 feet my heart is pounding its self out of my chest so it is not something I would likely need this side of the afterlife but it is a pretty amazing bit of thinking and engineering 