It works by checking your calendar to see if you’re at an appointment and knows when you’re on a call, and displays an available or busy status icon when other Truecaller users look up your name. Understandably, this only works when both parties have the app installed.
The latest version also integrates a dialer, which is a sign that the company is looking to kill off the standalone app it created for that purpose.
In addition, Truecaller will now be able to identify people in your call history, even if they’re not saved in your contact list.
I’ve found previous versions of the app to be useful for blocking telemarketers and unknown callers, but I wasn’t a fan of having two separate apps installed in order to see dialed and incoming numbers correctly identified. The update should help fix that.