I have a cheap Blackhawk holster mounted inside the center console. With the snap closed, that will effectively keep it in place during normal driving or an accident.
If I need to, I can put my carry pistol in it and just wear the holster I had empty, or take the holster off as well.
Doing that also keeps the "ok, where did I put my pistol?" issue when returning to the car from a prohibited location to a minimum.
At some point, I intend to get a "car gun", a cheap .45 or an old .38 and just leave it there all the time.