in my opinion, checking of your partners mobiles for the purpose of keeping tabs or "just checking", is definitely wrong. and honestly, using the logic that "whats the big deal if you got nothing to hide" is plain childish. so, if you have no use for the money in your bank account now, can i take it for my own use?
seriously, it doesnt mean that partners have to tell partners EVERYTHING just because its asked of them. whatever happened to trust in a r/s? of course, in the original post, obviously something is amiss which aroused OP's suspicions. there is a genuine cause behind his actions. but, if you are just snooping around poking your nose just to keep tabs on your partner because of your own insecurity and not because your partner is giving you cause for suspicion, then its plain disrespectful.
heartbreakman, i think its fairly certain there might be more than meets the eye to your wife's smses. you should have a talk with your wife on your concerns. assuming your wife is just developing an emotional attachment at this stage, if your wife is willing enough, the situation can still have an about-turn.