We've gotten a request on issue 13389 to add the ability to launch local commands (a voip client in that case). We've also suggested doing bug 4344 at the same time, to get a nice user interface for this.
Peter had an idea about this: First press: - Drop fullscreen - Launch the specified process when the button is first pushed, and keep track of the PID. Subsequent press: - Check if PID is still running. If not, behave like first press - Drop fullscreen - Restack so other application hopefully becomes visible
If we do this as a general feature, we should probably control it via adding special configuration entries, one for each command.
FLTK lacks restacking functionality, so it would be a bit of a hack to do this.
This is very odd functionality that doesn't really fit in with how ThinLinc normally is used. We also haven't had any requests like this since the original one.