Spoken like a true Ethical Sadist.

Here is a fantasy you might find entertaining. The client agrees to wear a device for say 3 weeks. After about 10 days he does a session with you which will include a lot of Tease & Denial with the device off. Then around day 17 there is another session with a good dose of T&D. However at the end of the session you hand him a book. It is an erotic novel, a very erotic novel. You order him to read the novel before the next session scheduled for the 21 day mark. At that session you will give him a test to see if he had has read it. If he passes the test he leaves the session with the device removed but if he fails he will remain in chastity for another week.