That is an interesting thought experiment. IANAL, but I'm pretty sure putting something on your head to essentially coerce information would be a violation of the right to remain silent. I don't know whether it would fall in the fingerprint vs spoken password space in terms of subject-to-search-warrant.
Fortunately this tech is currently very person-specific and have to be trained to the person. So to thwart it you'd just have to think applesauce over and over.
Fortunately this tech is currently very person-specific and have to be trained to the person. So to thwart it you'd just have to think applesauce over and over.