The main idea of this simple DIY Arduino project is to be able to determine the amount of time you spend inside and outside of your own premises. The device can be attached on your waist all day without obstructing your regular daily activity. This device will record your location history all day long, with a detailed report of the time spent indoors or outdoors.
MSP430 Launchpad from Texas Instruments is one of the cheapest microcontroller development boards (4.30 $), but it was lacking a free IDE (I mean free as in freedom, not as in free beer). Now there is Energia, an Arduino-like IDE for MSP430 Launchpad, which makes it easy to get started, no matter the technical level of the user.
Recently I saw the LOL Shield .. an Arduino Shield with lots of LEDs. This shield uses chalieplexing, a technique which allows you to drive a big LED matrix with a small number of I/O pins. If you’re wondering how does it work, here’s the key concept: tri-state logic.