Unique screen protector adds a physical back button to your iPhone (well, sorta)

A lot of people don't realize that iOS has had a built-in feature that allows you to swipe to go back within apps since iOS 7. It's faster than using a physical button. If you have a 6s, you can use 3D Touch to switch back to the last app.

 

I don't think you're doing it right. It works almost every stock app (the Calandar is the only one I could find where it didn't work). Try it in your Messaging, Phone, Mail, Notes, Photos, Videos and Music apps. It works in a lot of third party apps as well.