Well Jasper, I actually think its ok for her to look through his phone... he's got nothing to hide.
She's not cheating on him right now, so he really needs to turn the focus around to setting an example rather than being in affair-combatting mode...
Even if she won't let you look at her phone, I would still show her yours.. you got nothin to hide.. it may take her six months to get it and share hers, but who cares.. you are no worse off by setting the example so I say do it.... you can gain a lot by settin an example and you stand to LOSE a lot by not doing it.
If you want your wife to trust you and you want to trust her you have to take a FEW steps.. and sharing YOUR phone when there's NOTHING hidden in there ANYWAYS is a FREE step on your part... I say take it