I just came across this at Mistress Lori's website. It is a $15 box that snaps shut and needs to be broken to open. Great way to keep track of whether key was removed or not. However, I find sealing an envelope and signing it works well for us.
http://www.chastitytube.com/lockbox.html
Great way to store emergency key
Great way to store emergency key
0 x
"It is the mark of an educated mind to be able to entertain a thought without accepting it." - Aristotle