This is a simple magnetic stripe emulator.  Basically you can stick this into a magnetic card reader and emulate any stripe data you'd like.

How often have you sent off a message in a bottle, only to realise, as it floats out of sight, that you regret the contents of your message? Well, with the Text Message in a Bottle (TM) that will no longer be a problem! You can update your message at any time, just by sending a text. Fantastic!

I created this as a simple project for those just starting out in robotics. It is relatively inexpensive, requires minimal tools and is easy to build. Once finished you have an expandable robotic platform that fits in the palm of your hand and can be easily programmed in the Arduino environment.