Came across this app to control the LED display on my S3.

I've tried "Light Flow" in the past but had conflict problems with other installed apps.

So far Light Manager hasn't missed a beat and is definitely worth a looksee.

I have no experience with running Light Manager on an un-rooted phone so can't really comment.

https://play.google.com/store/apps/details?id=com.koo.lightmanager

More info here.

http://forum.xda-developers.com/showthread.php?t=1735331