The reason the courts find the production of passwords to be testimonial is that they are used to access potentially incriminating evidence the specific existence of which the prosecution is not already aware of.
Further, the Supreme Court Justice Clarence Thomas (with Scalia joining) said that the 5th amendment applies to, "compelled production not just of incriminating testimony, but of any incriminating evidence." https://www.law.cornell.edu/supct/html/99-166.ZC.html
The courts' definition of "witness" is what's relevant in addition to "testimony". Is your smartphone a privileged "witness"? I would think that to be the ultimate decision that needs to be made by the Supreme Court, and one that may in fact hinge on what person is next appointed to the Supreme Court.
Further, the Supreme Court Justice Clarence Thomas (with Scalia joining) said that the 5th amendment applies to, "compelled production not just of incriminating testimony, but of any incriminating evidence." https://www.law.cornell.edu/supct/html/99-166.ZC.html
The courts' definition of "witness" is what's relevant in addition to "testimony". Is your smartphone a privileged "witness"? I would think that to be the ultimate decision that needs to be made by the Supreme Court, and one that may in fact hinge on what person is next appointed to the Supreme Court.