In my experience as a manager, ANY kind of micro-level timekeeping or micromanagement is not only dehumanizing, but also an utterly unsustainable waste of time and resources and a recipe to let deadlines slip by.
How much time someone spends in front of their computer, how focused they are, and how their process works only gives bullshit metrics and teaches bad employees to game the system. By "squeezing productivity" you teach underachievers how to fake work while still underdelivering, while overachievers will get burned out quickly.
You'll fool yourself into believing that everything is "in control" but productivity will lower in a boiling frog effect that you'll only notice after several months of having everyone glued to their screens.
What I learned after failing: You need to sample a large interval in order to have ANY confidence on employee productivity data. So, it is better to allow employees to just be adults for longer periods of time (say, a sprint, or even a month) and measure them by their macro output and only act when they need you (aka be a real manager).
EDIT: Oh, and one more thing, if you don't have good metrics in place (like every programming shop ever), letting the OWN WORKER pick their metrics and give their own deadlines. This is a completely valid approach and will weed out under-performers like crazy.
EDIT 2: If you don't actually act on those macro metrics and pretend everything is fine, your team will resent you start looking for other jobs.