Syuzi @ Fashioning Technology writes:

Developed by Design Research Lab, Knit Alarm is a re-imagining of traditional medical alarms using contemporary materials. A “call for help” is triggered by either stretching the sensor woven into the left cuff or by touching the upper chest with your wrist. The sensors—I’m assuming are simply conductive thread— are knit directly into the cardigan itself.

It’s easy to make stretch sensors by knitting with conductive fibers. When the resulting garment is stretched, the fibers are pulled in tighter contact with each other, reducing electrical resistance.