iMessage is an iPhone’s inbuilt messenger. Did Apple really make it impossible to hack iMessage? Not at all! The most powerful way to open iMessage without them knowing is to use spy software.
There are multiple ones on the monitoring market. Some come under the sauce of parental controls, SMS trackers. But they all have in common – the ability to let their users hack instant messengers, including iMessage. Pick one of these to accomplish your goal: mSpy, Fonemonitor, Mobile Spy, iKeymonitor, Spyera.