The ResQue Me is available for peanuts unbranded from the online Chinese supermarkets.
Horrible tale here. My stepdaughters best friend suffered some sort blackout, shot straight across a dual carriageway and ended up upside down in a ditch full of water. She didn't manage to get out.
I've had one on my keys ever since, and sincerely hope I'll never need it. If it's hanging in your ignition, it's always easy to get to.