Re: Locked Phones
Maybe phones need an option for "if I don't unlock this phone for x hours, wipe". Then you only need to wait out that timeout before providing the code to police. If the timeout is short enough (12 hours would work for most) your lawyer can probably stall things quite nicely. By the time your lawyer's objections are overcome and you provide the code it is too late.
To prevent the "put it in a Faraday cage bag to prevent remote wipes" plan, a second option for "if no radio signal received for x hours, wipe".
Of course, there's always the "alternate unlock code that unlocks the phone and wipes it at the same time".
Just make sure if you keep backups of your phone to avoid losing everything when arrested that you use an offshore cloud provider. China would be a good choice for those of us living in the US/UK.
This may all be for naught though, as in general I suspect the most incriminating info on the phone will be call history and text messages, which the police can get from your telco....