Wearable computing. Prototype blood-measuring ring on a woman's hand. This affective computer has tiny sensors to measure the wearer's pulse rate and blood oxygen levels. These measurements are passed by a wireless transmitter in the ring to a receiver, which sends them on to another computer. From there, information can be stored for reference or, if something is wrong, medical assistance automatically called for. This ring could provide 24 hour health surveillance. Affective computers provide feedback about the wearer's physical state or behaviour. This ring was created at the Media Lab of the Massachusetts Institute of Technology (MIT), USA.