First and foremost i want to give ALL CREDIT to the original developer of this amazing app.
KeepScreen is developed by AxDroid LLC and hosted for free on the play store.
It has been forever since they last updated it and they were not responding to my emails. Their website also returns with an error so i am not sure if the company is no longer in business or if they just abandoned the app. (Its ashame honestly i love this app)
But there were a few quirks with the app. For instance, the app had to be manually started every single time you rebooted your phone.
Secondly i read people experienced the app would just stop working.. (I havent experienced this at all yet) But im guessing its due to android cleaning things up to free RAM.
Well i took it on myself and i was able to fix the first issue. After first launching the app and selecting the applications you wish to always have the screen stay on, and then launching the service, after a reboot the app will start again and you dont have to manually start the service.
The second issue i am currently trying to solve by placing a constant notification in the status bar. That is the only way to keep android from cleaning and killing processes.
The app is truly amazing, i have the Galaxy S3 and it has that "Smart stay" thinger where if you are looking at the screen the phone will stay on, well when im watching TV and i look up from my phone for a single second, they screen shuts off. I hate that, so i actually just use KeepScreen, set what apps i wish to always stay on, and then they stay on so long as that app is open and displayed on the screen.
Just download and install using a file browser.