If you think someone is a danger, get a warrant and subpoena their call records from the phone company.
Don’t go monitoring my activity “just in case”.
Ah, yes. First seek a warrant from what may very well be an activist judge who will call your request "racist".
That's what happened with the Minnesota laptop which contained information on the hijackers in FL. They weren't allowed to look at it and had to wait on a judge.
9/11 could have been stopped had they been able to look into the laptop.