Damien Consensual unlock procedure, that's an intriguing idea. I'd be curious what the wearers (well the ones who have a say about it, I'll never get used to the concept of involuntary wearers) here think about it.
In the context of BDSM play, it would probably considered a form of CNC. Best not proposed by the keyholder unless they are very close to the wearer. In the context of "serious" belt use, it could be argued that it is a valid measure to combat self-destructive impulsive behavior, but still, such arrangements push the boundaries of FRIES consent.