Here's how Google checks for lag on your Android phone

Yes, Google hates lag on smartphones as much as you do -- enough so that the search giant has a robot dedicated to spotting that delay between your finger input and what happens on screen. Meet the Chrome TouchBot, an OptoFidelity-made machine that gauges the touchscreen latency on Android and Chrome OS devices. As you can see in the clip below, the bot's artificial digit pokes, prods and swipes the display in a series of web-based tests (which you can try yourself) that help pinpoint problems in both code and hardware. This isn't the only gadget monitoring device lag at Google, but it could be the most important given how much the company's software revolves around touch. Don't be surprised if this automaton boosts the responsiveness of Mountain View's future platforms.

Engadget