I personally carry my cell in my chest pocket behind my notepad. I use an apple bumper and carbon fiber rear protection with screen protector in the front. Since our uniforms have a button for the chest pockets, I don't have to worry about if falling out while running. Of course, if I have to use force, there is always the chance of it getting crushed, but thats why I put it behind my notepad. With it between my notepad and armor, its fairly well protected.
Carrying it on duty belt is a bad idea because if you carry it on your right side, its going to get beat up by the seatbelt receiver, or radio stack (depending on how your unit layed out) If its on your left side, it could get struck by the door getting in and out of your vehicle. My department uses a mix of Crown Vic and Dodge Chargers. There is a little more room in the Ford, but definitely a slightly tighter fit in the Dodge.
Just do what I do... buy insurance on the phone, and try not to beat it up too bad. When working nights, or busy shifts, I remove the phone entirely and stick it up in the visor.
