what can I use to take time-lapse video with the screen off? I've tried so many iOS apps and wasted a bunch of money... none of them can do it. I want to leave my spare iPhone in front a tray of wheatgrass to document their growth over 5 to 9 days. I don't have a problem with the phone having to be connected to the charge all the time, but all those apps leave the screen on and that seems very dangerous for so many days, no? Thanks!