I know there's some controversy on the permissability of women wearing tefillin and that most poskim forbid it. From what I understand that is for women to wear tefillin for the purpose of the mitzvah of tefillin. Is the same true if they are worn as an amulet for protective purposes? Is it still forbidden?
The Mishna Berura (301 sk 158) quotes an argument among Rishonim and Achronim about whether a woman who finds Tefillin in public on Shabbat may wear them as amulets to "carry" them back to a safe place. The debate centers around defining normal modes of wearing clothing. He doesn't cite anyone who suggests that the Rama's exhortation (OC 38:3) of "מוחין בידן" protesting women wearing Tefillin would prevent the woman from "carrying" the Tefillin back to a safe place.
It seems from this that there would be no problem, but perhaps the Mishna Berura's case is unique as the safety of the Tefillin is at stake. On the other hand I don't know of any other case where someone would want to do this.