[Poohbah]

I have wondered whether there is an electronic signal that could be radio transmitted that could trigger the airbag.

Since the airbag is fired by electromechanical means--namely, a very violent deceleration moves the switch--that "eletronic signal" would have to accelerate a good-sized weight.

Point a phased-array radar at a ball-bearing and see if you can make it move...

[dark_lord]

Which simply means that a mechanical source activates an electrical signal. Here is an airbag schematic (not for real but a teaching example.) It appears to contain IC circuitry -- and IC circuitry if not properly shielded is susceptible to RF.