Spent the morning learning the best ways to create nice app-like interfaces for shell scripts on the three platforms.

Windows:

Used "Bat To Exe Converter" to create an exe: http://www.f2ko.de/programs.php?lang=en&pid=b2e

Mac:

Used Platypus. Found a number of things I had to work around to get it going properly. Tested on a couple of other Macs.

Linux:

Settled on a solution where the first time the script is run (or whenever it's run without a folder parameter), a .desktop file is generated, pointing to the path of the script (which can't be relative in a .desktop file). This seems to work OK. Parameters are passed to the script automatically.

This is now ready for testing on any platform.