The problem isnt my tablet or phone. I tried a few, including a nexus 7, a new, fairly high spec android phone and an iphone. I see no real difference between them. But like I said, even the official best case latency figure of 220ms, so even if no lag is added anywhere else, is more than twice what I find good enough. Well, its clearly good enough if you are shooting landscapes from 400ft. It isnt if you are chasing bigscale RC cars at <6ft altitude.
So yeah, Ill be adding an analog 5.8 GHz FPV setup to my phantom. Ill have to keep the gimbal tilt fixed or framing will become a challenge, but at least I'll be flying where I wanted to.
just test it. Shoot video of a stopwatch and record both the original and your tablet. See if you can get <250ms difference with the phantom within arms reach. Then double check the math I posted above, and you may see the problem.
For the record, my miniquads have a roll rate of around 3 full flips per second. 250ms is an eternity then, and with no autoleveling, so having to stop the rotation at the right moment, its basically unflyable.