Remote Chasity Monitoring

Force him to send you a photo on your mobile phone showing the lock on him within minutes of your request when you are not with him (interrupting him in something he's doing or when he’s travelling).  Give him instructions to have something else included in the picture (newspaper, or something) so that you can be sure the photo was taken in that exact moment on your request. 

Threaten him with severe punishment for non-compliance.