Air bags deploy based on a instant g-load, not vehicle speed. They will still deploy if your car is stopped and gets hit in the front.
Having driven a couple of my cars on dynos, if the car is not strapped down properly there can be some pretty large shock loads. I saw a big horsepower FWD Pontiac GTP pull its rear lower control arms out of their bushings on a dyno run.
EDIT: Chassis dynos car be very dangerous. I showed up at Superior's dyno in Anahiem as the paramedics were hauling away the dyno operator. The big horsepower Camaro he was running blew a driveshaft and it flew sideways and snapped the operator's ankle, which was hanging out the driver's door during the run. The driveshaft also knocked over a big Snap-On toolbox.