I'd love it if I could track the difference between how much time I estimate for a focus session, and then the time I spend on the focus session.

I'm a motion designer / illustrator, so for instance, if I planned to spend an hour illustrating a tree and then the illustration actually took 1.5 hours, I'd love to be able to see the difference between what I planned to do and what I actually did. Hopefully with this data I'd be able to track what kinds of tasks I consistently under-estimate.

Or also, if I planned to do a bunch of focus / break sessions, and then actually was on slack or YouTube, I could see the difference there as well, and perhaps pinpoint what activities are most distracting by looking at that data over time.