Relax, everyone. This is highly over blown. Yes, in some backward areas, you may be charged with wiretapping. And, yes, you'd have to hire a lawyer. But you'd beat the charge. The case law is quite clear that there is no expectation of privacy in a traffic stop or incident in public with a peace officer. Heck, they use that case law all the time in the prosecution of cases. Now, you might get caught an disturbing the peace or whatever local law indicated interferring with the duties of a police officer, but you can get that for 1 million different reasons.
And Califonia did NOT say it was OK to go through your cell phone without a warrant. They said that it is OK for electronic media (in this case, a cell phone) to be searched after it has been impounded as evidence as part of an arrest. They can also search your pockets and car after an arrest, all without a warrant (assuming you were in your car at the time of arrest, or similar circumstances).
Yes, police over reach and prosecutors are incented in the wrond way but if you are stopped, feel free to record the incident. If the PO objects, ask him to call his supervisor.