In a 4 to 3 vote (which is often the score in criminal appeals decided by the Ohio Supreme Court lately), the Ohio Supreme Court ruled that "[t]he warrantless search of data within a cell phone seized incident to a lawful arrest is prohibited by the Fourth Amendment when the search is unnecessary for the safety of law-enforcement officers and there are no exigent circumstances."
Read the decision in the case of State v. Antwaun Smith, 2009-Ohio-6426, here and watch the oral argument here.