the Fitbit mobile app
Kronos provides an analog stop watch (I know, the real god of time is Chronos, but I like this name better) with unlimited lap memory and hundredth of a second accuracy.
Hopefully, the controls are fairly intuitive. Pressing the start/stop button on the lower right starts or stops the timing. While running tapping the upper right button saves the current lap time. When stopped the upper right button clears the timer and clears all the laps. Tapping the list button on the lower left brings up a scrollable display showing all of the laps.
Tapping the center of the display switches between the stop watch and the current local time. Note that while showing the current time all of the stop watch functions are active and all of the buttons operate as expected.
Details and source code are available at the support URL.