here's a couple things i've found you need:
deadlift-for overall strngth and throwing people around.
sprints-for chasing people down (plus, there isn't any reason to run for more than a few blocks)
knuckle pushups-to condition the fist/wrist for impact (we've had 4 people break thier hands hitting people this year)
stretching/joint mobility daily-sitting in a car or standing at a crime scene for long periods of time tends to make ya stiff. i take strtching breaks every hour or so at work, just to keep from tightening up.
rotator cuff-again, fighting with people (we had one guy tear his rotator, and was off for about five months)
also, a couple things i found-protein bars are a lifesaver-i miss my lunch prolly half the days i work, so it's nice to be able to eat something high in prtein/vitamins instead of hitting Donutland.
the pistol belt is about 20 lbs, and is hell on your hips/low back. that's why so many cops have bad backs...again, streching and deadlifting.
also, forearms strength is nice when you're trying to cuff someone who doesn't want to go to jail. i have worked my foreamrs hard since i started lifting (10+ years), and when i grab on to someone, they usually realize they're not gonn aget away..
hope this helps. also, check out StreetBull's articles-he has really good points in there...