Computers should expose their internal workings as a 6th sense (Interconnected)
What about a scarf or collar so the back of your neck prickles when somebody is talking about you on Twitter.
Or a ghost detector for homes, restaurants, etc that glows when someone is “visiting” in Google Maps/Facebook Pages or looking through a webcam? Maybe it would be better to control the air conditioning to produce a chill, or play barely audible infrasound, indications that there is a haunting in progress and the veil here is thin.