-On- the forehead?
From the games we have (almost) played, only the poseurs and non-commited use external I/O electrodes. Actually, most shadowrunners/deckers have a jack that they plug their cyberdeck into. This is generally in the side of the head or the neck, but I personally like where my character has her jack. *grin* Let's just say that plugging in my Deck became an exceptionally phallic action...
LM