Product reviews from real people have shown time and again that GPS trackers have caught cheaters in the act. You just attach a tracker onto any of your spouse's stuff (e.g., their car, their bag) and you can start tracking their whereabouts. One of the best trackers on the market right now is Tracki. I've tried it and it works perfectly! You can go to their website if you wanna see their products. Trust me on this.