Update: The Dallas police officers union is pushing for body cameras too. The police chief has been pushing for them for some time, in fact they've been trying a few vendors' cameras out in the field. They're looking to ease the cameras into use, mainly to ease the public's sticker shock over the price.
I'm hearing more and more about police officers wearing body cams. I haven't seen a body cam video yet, but I've heard that some local police agency is using them. Common sense would tell you that officers would be less likely to use force unnecessarily or otherwise act badly towards the citizens with which they interact (Ferguson, Missouri?). This article discusses just that, but backs up common sense with an actual case study: in Rialto, California use of force dropped by 60% in the first year the officers used the cameras; citizen complaints against officers dropped by 88%.
Those are big numbers. Personally, I think these cameras are a win-win. Bad officers are caught red handed. Bad officers getting caught red handed makes potential bad-officers think twice before acting badly. Good officers who are wrongfully accused get vindicated. Complaints and use of force go down... all of this is good.
So why aren't these things the norm everywhere? Cost. At $300-400 a pop the cost isn't insignificant. Only bigger police forces could afford that, I'd guess. The initial cost isn't where the real problem lies, though. Storage of all that footage will likely be where the real money is made. Hopefully competition will drive the prices down and make this technology affordable. It ought to be universally adopted.