and in the drivers seat!!!!!
(dont run fast cap im slow and lazy!) 
i have seen this trick done on a chevy big block that was being used to power a generator. it had an electric fan bolted to a huge radiator mounted on the side not the front so the water pump pulley was fully exposed. it didnt have a tensioner so the belt had to be tight fitted without assistance, just like the vw belt. so the guy just used the same trick to fix. scarey as hell to think of what would happen if the screw driver was thrown back instead of pulled under...........
have also done similar to take belts of various other motors, but that was always the turn the motor by hand method or disable ignition and bump the motor over, never while it was running under its own power.
well, like i said...there's cars being designed with stretch to fit belts now. it's friggin ridiculous. in the case of that bug in the video, the generator pulley comes apart. in between the 2 halves, there's shims. that's how the belt tension is adjusted on those. on the "new" stretchie belts? need a tool to stretch em over. i just did an a/c belt on a mazde like that a couple of weeks ago.