The "Under arm" solution sounds like a reasonable alternative to a breakaway, but I can see at least three problems with that: 1. The "pendant" will eventually slide under the armpit, creating an abrasion point and exposing the kit to much more moisture. 2. It will be heaver and have larger skin contact surface. 3. In a free fall situation it is still possible to get a deadly neck cut with it and it is more "catchy" as it is way longer.

I see the rock climbers concerns legit, however I don't plan to do any serious rock climbing with it, and I cannot imagine a situation in my daily life (remember that's EDC item) when such a short necklace under the shirt could catch on any stationary object around by an accident. The only possibility it can pose a threat I can see is if it could be grabbed in a fight. But that's still not even close to a free fall situation, so I'll have time to pull off the lock.

Update: I've just double checked, the thread I'm using is not #8 at all, it's V-138, so that's only 22 lbs tensile strength. Multiplied at 8 strands it's a bit less than my weight, so it will break for sure just under my body drag. So the answer is yes, I do have a breakaway integrated in it