If oyu are going to work on forgiving your wife, then the best thing to do, is to do it the right way - get into marital counseling - make her hold her OWN self accountable for her actions, she gives you full acess to the bills, you can see her phone at any time, she has to keep you informed of her whereabouts at all times...she has to show true remorse and willingness to do what it takes to get back in your good graces - and not get angry/defensive no mater how intrusive you need to be for a while....whatever rules you set. As far as cell phone monitoring, if it is her phone and the bill is in her name - it's illegal. There is a reasonable expectation of privacy - if it is a felony or a misdemeanor depends on the state. If it is a joint bill, where both of your names are on it and you both hold cells through the same plan - then you have access to the bills as it is (or should) and you don't need to put monitoring devices on her phone anyway. It shouldn't matter WHAT she is saying to her alledged former lover - just the fact she is communicating with him would be enough to show she isn't respecting you. If there are any numbers you don't recognize, she needs to explain who they are until you are 100% satisfied it is above board.