Am I the first to think of the criminal side of things to this...I.e. Criminal mastermind is arrested, his/her cronies can remotely force a wipe/kill the device therefore completely destroying any evidence a law enforcement agency could glean from the device? Given that all iPhones supposedly encrypt everything? Probably wrong but it seems that side of things have been possibly completely overlooked?
The iPhone protects criminal masterminds from the police in exactly the same way it protect you from criminal masterminds. And there is no need for cronies to do a remote wipe. Use a strong passcode (not four digits, but ten digits or 8 random letters), set the iPhone to lock automatically after a very short time, and nobody can crack it.
For a search warrant, the police would actually need concrete evidence that evidence is stored on the phone. Saying "he's a criminal mastermind, there is surely same evidence on the phone" won't do, and the criminal mastermind's lawyer will (rightfully) tear anyone apart in court who tries something like that.
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Personally I don't care if a "mastermind" has his phone wiped. My data belongs to me. Besides a real wipe takes hours and hours, the iphone probably just marks the data for deletion and never overwrites it so its all still there.
Wrong. All data on any iPhone is encrypted. The encryption key is stored on the device (it is itself encrypted, obviously, and can only be encrypted by you entering the passcode). For safety in case it is accidentally destroyed, it's stored in two places. Erasing these two places is all it takes, and after that the data on the phone is not readable by anyone.