You may have heard that motorcycle makers have been experimenting with airbags on bikes, but a more interesting development is the airbag riding jacket. There are several of these on the market from companies including Armored Air Jackets and Hit Air. Typically they use pressurized gas to inflate air cushions built into jackets or vests that protect some of the rider's most vulnerable parts. The jackets are activated by ripcord-style devices that sense when a rider is thrown off the bike. They stem in part from research into airbag-equipped racing suits aimed at professional motorcycle racers. But with more than 4,400 motorcyclists killed in crashes last year, interest among street riders could wind up driving sales of riding gear with built-in airbags.