I'm going to be that guy: The flip isn't really that difficult, probably less difficult than doing a double-backflip. All you have to do to get your body to flip around is look in the direction you want your body to go. Just turn your head, that's it. Your body will follow where your head turns. Once he spots the bike, he just keeps his eyes on it, and his body whips around. The hard part is grabbing the bike and getting back into riding position. Oh yeah, and having the monster balls to try this in the first place.

EDIT: Also, the video the GIF is from looks like it was shot at either Woodward camp or Lake Owen camp. In addition to offering things like BMX, skateboarding, etc, these camps also have gymnastics facilities for gymnastic camps. They have tons of trampolines and foam pits where people can learn this stuff. They have ramps that lead straight into foam pits, so people can figure out how to do this crazy shit without risking their lives just to get it down.