Why not tattoo it on your arm, there is precedence for that.
For goodness sake, the younger generation is getting tattoos in places that an old-time lascivious sailor wouldn't even have imagined. Why not right on one's forehead, easily seen? Or on your eyelids, only displayed when you wink?
In fact, Bill Gates has an app for that!
Those who do not know history are destine to repeat it.