Try and make it visually appealing and allow me to set which sites are in what category when i go to a new site also also make pomo an option and tie it with habitica if possible so that would maybe give u a push idk about how one could connect to the service but integrate the thing to other apps which give api and whatever otherwise a nice extension.
for eg look at time tracker its a brilliant extension which looks really good try to get into firefox recommendations and have a x factor time tracker has that x factor with ui u can have connections and integration as your x factor

Awesome extension. Considerably increased my productivity. Thanks Dev!

Excellent tool for staying focused during work hours.