His (and often a secret, 2nd) cellphone is usually all you need to monitor; people caught up in affairs use their cellphones like a crackhead uses crack. There are other ways, and yes many are unpleasant but personally I did what I had to do to protect my family when my wife was having her affair. Being able to confirm her promise of continued no-contact was imperative to me, and she did slip up -- twice. But we got thru it, and today are happily married 7 years later.
I do think the MCing will help you. Among other things, the MC can be the "bad cop" and let your formerly-wayward husband know how important no-contact and transparency are to you, and to your likely success at putting Humpty Dumpty back together again here.
