How to do this for all but free and discreetly?

So i want to be able to record what my fiance is doing at this "friends" house I don't trust it at all what ever goes on over there. Is there a way to discreetly record him without him knowing or a way to record it through his phone without him knowing and it has to be either real cheap or free. Is there a way to do it through my phone. He has an iPhone 4s with the ios.7 update I have the note 2. Can I transmit it to a laptop.

I'm sorry, I've literally been thinking of a way to do this for like 20 minutes and I'm drawing a blank.

Maybe if you know any super smart tech nerds you can get them to implant a microphone monitoring chip in his phone and you can listen to everything he says while hes gone. Idfk

There may be an app that would turn his phone into a recorder. It won't be free and it may not even be legal (privacy laws differ from state to state.)

Anyways, if you can't trust the guy, why are you marrying him? What, you think he's going to change into Mr. Super-Duper-Trustworthy after he says "I Do"?

No, here in fantasy land even that isn't possible.

If you can't trust her/him move on - what kind of relationship will get better if you are already engaged?
http://www.brickhousesecurity.com/category/alarm+systems.do

If you can't trust him now. You won't trust him ever. Move on and leave him.