[Equinox]

You can jailbreak and backdoor the target iPhone, though this is illegal, which if you're coming here you probably don't care.

Realistically, if you don't trust your husband, or think he may be cheating on you, you can do a few things. First off, prehaps confront him about the situation, if you have a steady relationship with him, and I'm assuming that you do since you're married to him, then this should be something that is okay.

If you are afraid to talk to him about it, you can hire a private investigator, slightly less illegal, as far as I know, than backdooring a phone.

However, I think you should think a bit more deeply about the situation at hand; "He's my husband, and I love and trust him, would he really do this to me?"

Honestly, if you can't trust your own husband, then you shouldn't have gotten with him in the first place. And I am by no means trying to be rude, but you should really contemplate before jumping to conclusions, as it doesn't appear you have any hard evidence on this, rather just assumptions.