Mistress Lena has just written an excellent description of her long-distance keyholding techniques and locks. It's a short but interesting read and can be found here: https://lenaloveslatex.com/uncategorized/long-distance-chastity-made-real/ I can vouch for the security and the usability of the locks!
Interesting. But I have never heard of it before and didn't find anything when I was googling after a solution like this. Is it new? But you have tried it?
Yes. She has me under lock and key from time-to-time. The locks are secure and work really well. She's also a natural keyholder if that is what you want. I know she sells her locks if you have your own keyholder or she can optionally provide keyholding.