Remapping the volume keys to turn on the screen only work sort of, most of the time it would take a few minutes to actually get the phone to wake up. It's almost like when the phone goes into deep sleep it sleeps whatever controls the volume keys. The best option for me has been Gravity Screen Pro. I've been using it for about 2 weeks now and it has worked flawlessly, no need to remap anything, you don't even have to touch the phone to turn it on. Putting it in your pocket automatically turns the screen off, and turns it on when you take it out of your pocket.