I wish every developer had one of these. When you think about it, it's crazy that our devices don't have built-in APIs for measuring this stuff. The latencies are all known exactly at the time the various pieces of hardware are designed, but when the system is integrated that information is lost and suddenly there's no way for the software to know exactly when the finger physically touched the screen, or exactly when the pixels start lighting up, or exactly when the speaker will start vibrating.

In most cases it actually takes less time to send a network packet to a server thousands of miles away than it takes to change a single pixel on the local display. Wouldn't it be great if you could measure the display latency as easily as you can run 'ping'?