keep (one's) finger on the pulse
To maintain an awareness of current trends and happenings in a particular place. Sara keeps her finger on the pulse of nightlife in the city, so I would ask her where you should have your birthday party.
have/keep your finger on the ˈpulse (of something)
know all that is happening; be aware of new developments in a particular situation: Successful politicians need to keep their finger on the pulse of the voters.A doctor takes your pulse by putting his fingers on your wrist and counting the number of times the blood beats in a minute.