Since this seems to me to have more to do with support to your thighs as opposed to anything really to do with your butt/ass , I think a more proper name would be the THIGHBOARD or the THIGH-A-RANG.
My thoughts on possible solutions to make this a retractable deployment concept for the bike would actually have the "wings" swing out from the sides of the seat, like those swept wing fighters. If positioned right, it might even be possible to "override" the system by lifting your rear slightly and using the area right behind your knee to push back and swing the "wings" out of the way , allowing one to get a foot down if needed.
The other idea about having the them hinged so they fold up, powered by pnuematics, with a sensor that retracts them instantaniously if a certain amount of front brake is applied , seems sound too.
Inflatable "bags" seem like a good idea too, but not sure how quickly one can be deflated if the need arises. Something that makes them deploy/retract in nano seconds is the way to go.
KM