This is a cool project. I thought about building something similar a few years ago when I was doing a lot of consulting. The most annoying part of the work was accurately billing clients when some days I'd switch between several projects.

Here's a few things that could make it super useful:

* Track time spent writing email by contact * Track hangout/skype/etc by contact * Track time spent on code per project * Connect phone records to tie in the time on the phone with contacts

Good luck!