In fact, some mobile phones have wonderful stopwatches built in. My SonyEricsson K750 and many of its relatives have a stopwatch with multiple laps: by pressing one button, you stop the current lap and start counting the next one. On the screen, you see the current lap and the total elapsed time, and the joystick allows you to scroll to past laps. What else could one wish for? Just hang it on your neck, or else you may have to fish for it all over the cockpit.