A team from the University of Washington has developed a system that allows passcodes to be stored in your clothes without electronics, courtesy of a patch of magnetic fabric that can be read by sensors at a door or vending machine. You don’t have to bring on-board electronics or sensors all along.
Conductive thread has been used to make health-monitoring wristbands and Solar Bikinis, but the UW team realized the material wasn't just useful for conducting electrical signals: it could be magnetized to store digital data like a hard disk. Codes can be written to the conductive fabric by rubbing magnets on them to generate ones or zeroes in certain sections, which can then be read by simple magnetometers to verify a specific signal and grant access to a computer or approve a payment.
Perhaps the most important feature is that all the electronics are in the readers only, so there's no need to embed them in the clothes themselves. That means the material can be thrown in the wash without worry, which is more than can be said for other smart wearable’s that are weighed down with bulky electronics.
Future work is focused on developing custom textiles that generate stronger magnetic fields and are capable of storing a higher density of data.
Source: http://www.washington.edu/news/2017/10/31/how-to-store-information-in-your-clothes-invisibly-without-electronics/