Requiring cameras would assist in ensuring that each and every officer is not only held accountable, but also protected from false abuse-of-power claims.
While on duty officers should have the peace of mind to know that everything they see is being recorded so they will always have an unbiased witness. This would also aid in prosecuting officers who might be taking advantage of their power as civil servants.
This would definitely be an expensive endeavor as there are somewhere between 700,000 and 1,000,000 Law Enforcement officers, however only officers currently on patrol would need to be equipped at any given time. The price of a medium-high end HD camera runs between $200-300 for a civilian. If 200,000 of these were purchased, it would total $50,000,000. 2/3 the cost of 1 F-35 jet.