At some point, we concluded with the key holder that the spare key should be available to the slave in case of extreme situations. I built something with Dog & Bone Lock Smart lock and small steel box that my owner can conveniently control with a mobile phone. The spare key is in that little steel box. I have one unlock enabled all the time, so I can unlock that Lock Smart lock, if necessary, on my own mobile phone. However, this will immediately inform my owner. My owner can see the location and the time of opening. The whole is convenient and travels with me, for example, on business trips, etc. If I opened the lock without permission or without reasonable cause and explanation, I would be in great trouble. My owner, My Wife (KH), has kept me locked out since the summer of 2016. She uses me and the penis to satisfy herself just when She feels like it. Luckily, I am hanging at the other end of that penis.
In the unterest of safety, my spare key is on a tiny fold chain, secured tightly around my neck and locked tight with crazy glue. In an emergency, the chain would be broken and the key available, but could not be easily restored. It's been on for close to 3 years now.