Thunder Stopwatch

Thunder Stopwatch is a toy app that can be used to estimate the distance to a flash of lightning.

Features:
The app provides a simple stopwatch with large controls.
The app automatically estimates the distance sound may have traveled.
The app keeps a history of recent times and distances.
The app displays a plot of recent distances.
The app can be configured to display distances in English (mi) or Metric (km) units.
A help section explains the simple physics used to estimate the distance.
A help section provides a set of must know thunderstorm safety tips, plus links to publicly available safety fact sheets.
Source code available under GPLv3 (https://github.com/forrestguice/thunder-stopwatch).