An interesting holster made by Stellar Rigs:

These were announced by the manufacturer on rec.guns recently:

Our Kel-Tec neck chain concealment rigs were developed originally for
LEOs to carry the back up gun under their vests. Over time a number of
“civilian requests” had us make a vertical version for better
concealment. Now comes the “Extreme Duty” evolution. The most popular
question by phone or email is “how well does it hold?” Our standard
answer is “fine for cruising around in you car or walking but not well
enough to jump out of helicopters or off fences – is that what you want
to do?” The answer is usually no – but just in case.
We are now making “Extreme Duty” versions in Black and the sexy carbon
fiber laminate and they hang on almost as well as the NAA mini-revolver
models. In fact, You nearly have to “force load” them. Yeah, they hang
on good !

Personally I think the chain looks too thin and I could not carry a gun pointed to my chin, holster or not.

You may say that is superstition, and maybe it is, but I know of many cases of people shooting themselves in the foot while practicing for IPSC when drawing from holsters. I just would not feel comfortable.

UPDATE: I posted this in a hurry. Links to the manufacturer and rec.guns discussion are added.