In Android you can go into settings and change your screen's timeout. I normally keep mine set to 30 seconds which means if I lay my phone down without putting the screen to sleep it will time out in just 30 seconds saving precious battery life. This becomes an issue when trying to read if you don't touch your screen for 30 seconds the screen turns off, you have to wake your device, sometimes you have to reenter your lock pin. That can get old quick. Samsung attempted to fix this with smart stay in some of their devices. The screen stays on as long as you are looking at it. I have not seen a feature like this in any other devices.
KinScreen seeks to solve this problem. KinScreen senses motion, proximity, and tilt angle to keep your phone's screen on while it is in use. If KinScreen senses that your phone is not in use it turns off the screen saving battery power. You can customize the app to work how you need it to work. Head to the link below for the download.
via XDA