I am working on a time tracking app. I use it to keep track of time spent vs my estimates, and also just to check my actual working hours. It's fully local—everything is stored in localStorage — but I do have plans for some optional syncing so it can be used on multiple devices.

It has helped me a lot to keep focus while working and track distractions. It might be too tailored for my needs, but have a look: https://zookeeper.fyi