I've recorded incidents before and almost been body slammed to the ground by cops for doing so. Sure would be less intimidating to them, if ya had the right shirt/jacket front pocket that ya could place the phone into, so you're not pointing it at em like a weapon.
Caught some action a few years ago (right up close, I was high as shit on a hash log joint) of them puttin the smack down on some kid who actually tried to run out of their paddy wagon at the Ann Arbor Hash Bash. kid was already cuffed and racing away, arms already hand cuffed behind his back, funny as shit watching him run like that... man were they pissed off. Another cop saw me filming and smashed me hard with a shoulder slam and warned me to leave.