Touch Trace Mirror (by Schmeer et al 2011)
"Touch Trace Mirror" is a mirror which enables leaving a message on a steamy bethroom mirror over a distance. It is a set of two bethroom mirrors, one to be placed in each partners apartment. Writing a message on one mirror will result in the message being sent to the partners mirror, where a light will emerge on the mirrors surface. If the partner places a finger on the light, it will move, letting the partner trace the message that his or her loved one wrote.
Reference: Schmeer, J., Baffi, T. 2011. Touch Trace Mirrir: Asynchronous, Collaborative Messaging as a Concept for Creating a Relatedness Experience. In TEI'11