I used this to write papers by putting in how many words I needed to write and how many words I had written into a web app that I made for pacing. I made a widget for my watch that shows me if I am on pace with how many steps I want to take every day. And the big one, using it to pace out when I spend time on distracting apps on my phone. If the amount of time I have spent on distracting apps is behind the pace, then I can use the app otherwise it kicks me out.
I'm sure they are more applications I haven't thought of. I haven't made the code public yet, but I could if people are interested.