video://www.youtube.com/watch?v=w4uhn5_0RkU
Here’s a fun little hack that will allow you to spoof most magnetic stripe readers including your local groceries’ credit card reader.
This instructable demonstrates how to use an electromagnet, a simple amplifier circuit, and a personal music player to induce signals into a magnetic stripe card reader, causing it to think that you have swiped a card through it.