Get something like one of the Olympus Tough point and shoot (or similar water and shock resistant camera). Keep it in your jersey pocket. You can grab a shot within a few seconds, with practice. Water resistant means you don't worry about sweat corroding the camera, shock resistant means there's a decent chance it'll work if you DO drop it. Point and shoot cameras generally have better optics for zooming in than your cell phone -- and almost everything I want to shoot is further away than ideal, so I need that zoom capability. YMMV, of course.