That is the iButton. Kinda looks like a big watch battery, doesn't it? Well, the iButton is actually a pretty nifty little gadget. Crammed inside of that slick casing is a unique data-logging solution for tracking temperature or humidity. It includes the power source, memory, and sensors necessary to log data. It is small and rugged, so it has a wide range of indoor and outdoor applications. When you're done logging the info you're looking for, you snap it into a connector and plug it into your laptop and - boom! - information galore. But, for a product that is so awesome-ly portable, wouldn't it be nice to have an equally portable way of programming the iButton?
Enter the Portable Data Logger Programmer from SparkFun customer Jeff Miller (author of the blog Arduino Fun). This is a great portable way to harness the unique power of the iButton. Using the iButton cable, you can attach your device and program how you want it to log data without dragging your laptop into the field. If you want immediate info, attaching the 1-Wire Temperature Sensor (also from Maxim) will allow you to view temperature in real time. Jeff's programmer uses an Arduino Pro Mini 328 as well as a SparkFun Project Case. Check out the video below to see this awesome project in action!