I wanted to use a magnetic car mount for my s4 mini, but it would go into sleep mode every time the magnet went near. After a lot of research I found out that this is because it thinks you're using an 's case', which when shut uses a magnet to put phone to sleep. You can't disable this, and I installed loads of aps to try and disable magnetic sensor but you can't without rooting the phone. Answer in end was really simple, the magnetic sensor seems to be in the middle of the phone. So I placed the metal sticker on the bottom of the phone and use the magnet there, it works. Wanted to post this as took me far to long to work this out!