A sign that activates a button, lever or the like. The sign will activate the button or lever even if the user does not have perms to the area.

[Activate]
(Price to activate)

Uses:
Theme parks, museums and other places that would like an entry fee or to count how many visitors it has.
People are so creative that there will probably also be other cool uses :)

Hope I am not posting something that has already been suggested.