Although self rescue is one consideration I can only mention that it is not always about self rescue.

If you can reach the bottom of your seat while sitting, I would clip a large carabiner around where the seat attaches to the rail in the front, then a short loop of cable to secure the ResQMe to the 'biner. It should stay in place, and yet be accessible. Hopefully.

Yes, my primary reason for buying a seat belt cutter and for carrying First Aid is to help others, not myself.

I tend to happen upon things, like stray dogs. That's why I carry extra leashes, too.

I tied one of those cheap envelope openers, with a razor blade, onto the seat belt, near the buckle, with some fishing line. Since they are so light, I don't think it needs a strong line to attach it like some heavier tool would need, even if there was a car crash, and the string is weak enough that a hard tug can snap the line.

Anyone think an envelope opener wouldn't do the job of slicing at least one seat belt? It seemed to go through an old scrap piece of backpack webbing easily enough. Not like a hot knife through butter, but not difficult either.

I think the envelope cutter would do fine, but I'm not sure I could snap fishing line. You might want to practice that...

You might be suprised how much strength you have once that adrenalin kicks in

that's a good point about the mirror possibly leaving the scene of the accident...

I don't personally like things hanging round my neck & no way would wife do it either, so I'll have another look & see what alternatives we have.
Also will add a few more ResQme tools to allow passenger, 2nd row & 3rd row access.
Maybe one in the cargo area too. (SUV/mini-van crossover)

My buddy keeps a razor-sharp Kabar USMC knife attached to his roll cage right next to him. I asked him about it one day and he explained that he had a rig catch on fire once and he almost didn't get out of the belt. Good answer.

I keep a knife in my front right pocket 24/7 and have a razor knife in my Jeep just in case.

Also keep in mind that on the ResQMe, it pulls right off the attachment ring with a good tug. I wonder if a sharp collision would separate it and scatter it throughout the vehicle. The attachment from the vehicle to the ring might be a secure one, but from the cutter to the ring is not.

I have the CRKT MAK in my truck at all times.

Word of warning,, take it out before you do a car wash! LOL that was an expensive lesson.. ofcourse my truck isn't exactly inconspicious either.