alt Hacker NewsIf such technology actually existed I don’t think the fifth would cover it without a SCOTUS ruling. You have to actively plead the fifth to invoke it. A machine that could just read your thoughts would get around that the same way they got around the fourth by the interpretation that any information you exchange with a third party is no longer protected, in a world where refusing to ever do that would leave you destitute.
It's already been decided by SCOTUS that things like heat imaging require a warrant, and that arbitrary scanning without a warrant (or presumably also probable cause) is a violation of the 4th amendment. This technology (still science fiction) would likely get similar treatment using the existing precedent about how new technologies can be used.