The idea here is that the belt wearer should have an emergency key within reach, but that (s)he should not be able to access it without breaking something. This is especially necessary if the belt wearer and keyholder are separated by distance.
1) Someone on another forum suggested the idea of putting an emergency key on a thin chain around the wearer's neck, and then locking the chain with a small padlock at the back. A good idea, but there is always the risk that the belt wearer or his/her lover might break the chain in the heat of passion, where no true emergency exists.
2) Many years ago, Popular Science magazine had a brief mention of a product called the Key-Sure Key Vault. It was a small plastic box with a drawer that would slide in. Once you slide the drawer in, the box cannot be opened without breaking it. The article suggested that you could use this to give a trusted neighbor a set of emergency keys to your house.
3) One of the things I miss most about the old, original Access Denied company was their tiny key vault designed to be worn on a chain around the neck. Similar in concept to idea (1), but I guess the AD product would make it impossible for the wearer to make or obtain a duplicate key. I was trying to locate the original web page for you via web.archive.org, but I couldn't get it to come up.
4) Chrono Vault from Dream Lover Labs
http://www.dreamloverlabs.com/chronovault.php
There is at least one competing product on the market, but I have a sentimental attachment to this one.
The vault can be purely timer-controlled, or it can be opened via an encrypted message sent over the internet.
