It's fun to measure these sorts of numbers for all kinds of devices. You don't need equipment that is too fancy, a Casio Exilim EX-ZR10 (cheap!) is good enough to get numbers within 4ms by framecounting the high speed videos. I personally find input lag on Android devices infuriating, I wish more attention were devoted to fixing it.
It can be even easier than that: I wrote a benchmark that allows you to measure input latency for web browsers without any specialized hardware or cameras: http://google.github.io/latency-benchmark
Of course this technique can't tell you the hardware latency of a touchscreen or display, but it can measure all of the latency introduced by software, which can be quite significant (and as a software developer, the software latency is the part you can actually influence).
