I must admit that this a fantasy idea, but it might actually be feasible for someone who likes predicament bondage and chastity but does not have a keyholder to secure them or decide on their chastity sentence. It does require some technology for the timer system. There are a great number of variations but the basic scheme is as follows. You need some sort of predicament bondage such that one position is stressful and the other position is comfortable but operates an electrical contact. You lock on your chastity device, lock up the keys then get into the bondage. So long as you maintain the stress position nothing happens, but if you relax into the comfortable position the contact is closed and your chastity sentence starts to increase. After a suitable period you would be released from the bondage, but left locked in chastity until the sentence is complete. One way to do it would be with an Arduino as the timer. The Arduino would be in a safe also containing your keys, with power fed from outside. I don’t think it would be too difficult to program it to increment your lock up time whilst you were in bondage, then keep the safe locked until you were due for release. It would then operate a relay to reconnect the lock solenoid and allow you to open the safe. You could also use it to operate an electromagnet for your bondage release or you could do that with a separate mechanism. Of course you adjust the bondage period and rate of increment so that you suffer a challenging predicament or a challenging lock up or something in between. As for scenarios, perhaps secure a chair to a heavy object so it can’t move. Have your ankles fastened to the chair legs, your waist fastened down to the back of the chair seat, so you can raise yourself off the chair but can’t stand straight (that could also make sure you could not fall forward if the restraint is strong enough). Your hands would be suitably restrained and there could be a pressure pad on seat for electrical contact. Alternatively, perhaps an arrangement where you have to keep tugging a cord attached to your nipple clamps to prevent adding time to your chastity lock up. There remains the question of whether you have a display so you can see your lock up time increasing or whether you can do without that complexity so you don’t really know how long you will be locked. A compromise would perhaps be a light which flashes for every hour added. Finally, of course, there would be the need for backup and emergency release etc.