If you mean CLI by desktop app, then... It strips out one of the most annoying parts of doing exercises for people who already have tools and like them... navigating to a website, using some crappy browser editor, file browser, and all that. No copy/paste.

This is the workflow:

    Ask for a new [language] exercise (it selects the next one for you to work on and downloads a test file and readme)
    Work on exercise locally in whatever environment you want
    Submit exercise and fetch the next one