An app that will let you see your partner's texts?

Okay, before I get all kinds of comments me AND MY BOYFRIEND decided to try this out. There's this app called "couple tracker-spy your love" where you both install it connect with each others phones and basically it lets you view your partner's texts, phone calls, etc. But that is only for android and my boyfriend has an iphone. We wanted to try this just to seehow it goes, so please can someone help?

I can't imagine why anyone would want that.