While I generally support this, I do see possible drawbacks for police officers. Video, photographs, and audio recordings only show you what the creator of them wants to you see/hear. Even a 100% appropriate application of force could look like abuse when you don't see the confrontation leading up to it.
However, I recognize that such cases will be a minority. Most of the time, the cell phone footage catch legitimately abusive or questionable police actions. However, police brutality seems one of those crimes where everyone would remember the accusation but no one would notice the acquittal, so yeah. I'm not sure how I feel.