This page is for details of USB footswitches that can be used to control any application, but may be especially useful for audio, e.g. to stop/start playback or to enabale/disable effects.

This thread discusses one- and three-pedal switches from PCsensor that work on Linux, but have to be configured from Windows. The software does not fully work on Wine as it does not see the unit. Each pedal can be configured to send any key combination or string. Once configured, the settings are permanently stored.