Sure. But probable cause is necessary for you to open your trunk or your pda as well - 'plain sight' rules apply. If you get pulled over on a traffic stop, there is no probable cause, and no warrant would hold up... Unless they found illicit drugs for instance (by plain sight), whereupon, while you are sitting in jail, a warrant will be issued to search your home your car, and probably electronic information services and devices.
Again, if its in your mind (like a password) you cannot be compelled by law to divulge.
Right, which is why I said that nothing incriminating should be kept on an electronic device, anymore than it should be kept on a piece of paper.
On that we agree. The rest is an open question, for now.