Warrentless cellphone searches are reasonable if only it falls within a specific exception to Fourth Amendment's warrant requirement. See Kentucky vs King. I looked up Kentucky vs King on wiki. TL;DR warrantless searches conducted in police-created exigent circumstances [0] do not violate the Fourth Amendment so long as the police did not create the exigency by violating or threatening to violate the Fourth Amendment…
I only read the opinion summary and the concurrence, but from the summary: > And, at least as to remote wiping, law enforcement currently has some technologies of its own for combatting the loss of evidence. And from the rest, once the officers have removed the phone from your person, there's no longer a danger of you wiping it. Of course, I don't want to suggest in the least way that officers will actually /follow/…