How do I spy on all activities on a iPhone without them knowing it?

How do I spy on all activities on a iPhone without them knowing it? - 1

Install a child monitoring app, I recommend TeenSafe.

Note: If you don't own the device (not a parent/guardian) then it is illegal to install said apps. Doing so is punishable by law.

A woman thought her husband was cheating so she installed a spying app. Turns out he was in fact cheating but he was able to take her to court for unlawfully spying on his device. She was found guilty and fined a huge amount a long with a restraining order.

Edit: TeenSafe allows you to view text messages, call logs, phone location, web history, view installed apps and also view app messages such as WhatsApp and Kik. It's pretty much an all in one monitoring tool

Didn't mean to assume you're spying on a partner either, many people come here asking this to "catch" their partner cheating.