The MOD pedal is a full hardware audio plugin processor based on Arch Linux, JACK and the LV2 plugin standard.
It also has MIDI-in, and a host of synths under the "Generators" tab, making it a tool of choice also for keyboardists (and virtual drummers, etc.).
According to various reports and screenshots, there is an application in witch you compose your plugin chain(s) (and setup witch plugin parameter the HW buttons control) before you push it to the MOD pedal to rock away.
The MOD-app (and its front-end MOD-ui) is the "desktop" version of this application where the chain is actually functionnal ; It exposes the inputs and the outputs of your soudcard, and you just insert plugins in between.
It also exposes your MIDI hardware ports as well, allowing you to build a killer synth by just drag & dropping the modules.