This probably isn't a great test case to get up in arms about. Here's the opinion:
http://www.thenewspaper.com/rlc/docs/2011/ca-phonesearch.pdf
Some things you'd want to know before formulating your own opinion:
* Since at least '73, the law of the land has been that after you're arrested, the police can without a warrant lawfully search you and the immediate area under your control. The lawful objectives of that search are either officer safety or preservation of evidence. If you're arrested while driving a vehicle, and either of those objectives militate a search of the passenger compartment of your car, the police can search the passenger compartment of your car.
* The argument was made here in an earlier hearing that the cell phone search occurred as part of an "inventory" search; this is one of the contexts in which cell phones were claimed to be a "container". But the controlling appellate opinion here rejected that interpretation; the police cannot search a cell phone to "inventory" its contents.
* But that is a moot point if you are arrested, because the police are explicitly entitled to search your person and your car for evidence if you're arrested. Don't get arrested! Here we have the second "phone-as-container" context: the phone is a container for evidence of crimes. It's this interpretation that the appellate court affirmed, and reasonably so!
* More importantly, in this particular case, this guy was screwed from the get-go. He was arrested for driving a car without a license, for which he could not document lawful possession, after doing 90MPH in a 65, on suspicion (later validated) of being under the influence, accompanied by a clearly intoxicated passenger. When the police searched his car incident to the arrest, they found a loaded gun in the car under the drivers seat, along with drug paraphernalia. Then they found the Blackberry with the screensaver set to the guy holding two assault rifles. Face it. That phone was getting searched. The notion that searching the phone pushes the bounds of "incident to arrest" searches is at best a technicality; under the same pattern of facts, a warrant for the search would be a no-brainer as well.
* ...but it seems extremely dubious to argue that this is even a real technicality. A search of your car is a big deal. The police are not lawfully entitled to invade the privacy of your car without reason. Getting arrested is a big deal. The police are not lawfully entitled to arrest you for no reason (there is a world of difference between arrest and mere "detention"). The search the police get to conduct when they arrest you is explicitly not limited to officer safety (like the weapons search frisk of a Terry stop). This guy's lawyer argues that the phone search was out of bounds because of an expectation of privacy. What expectation of privacy? They're in your car. They found your gun and your secret drug shit. Your privacy is largely out the window. Your trunk might, for a few minutes, be out of bounds because it's not necessarily your trunk. But the phone with your dumbass picture on it holding assault rifles is clearly yours.
Someone downthread had the right practical response to this: lock your phone. There's no secret software the police have that will suck all the info off an iPhone with a 6-digit PIN. Politely decline consent for searches. Do not get in a police officer's face; if you give them a justification to arrest you for any reason, all bets are off. Don't get arrested.