I can say this for sure.. you can't have both of the following options at the same time:
A) Impenetrable security on your devices
B) The ability for law enforcement to check any device and potentially stop terrorist events using the information
So chaps, make your decisions...
I'd personally prefer option B. and take the hit on my own personal security.
If you're stupid enough to note your bank details down etc (even on a locked phone) then really you're asking for trouble...