The car running over the guy's hand is just a gimmick.
Car tires are wide, much wider than the bike tires we are used to, and they spread force out a lot across the ground so the amount on his hand really isnt that bad. Also the car rolls over his hand gradually, it wasn't an actual 'impact' with all the high forces you'd get from dropping and suddenly stopping.
and +1 on the earlier helmet comment
It won't stop inertia from snapping your neck, which is really the bigger problem.
If you really want to dissipate inertia you need to slow the object down over a longer distance. No matter how squishy that gel is, I just don't see that kind of distance being available with the thickness its made in...