Computers are reaching new lows. Low prices, low size, and low thresholds for intraductory use. Devices such as the Basic Stamp and Arduino are available from Radio Shack, with starter kits under $50. These are different from a Raspberry Pi in the way that a mainframe is different from an old Apple II. The mainframe and the RP are great for programs that deal with files and data, but can't interact with the real world. The BS (and kin) and the Arduino are made for the real world; to make measurements and control outputs. No high lever driver or interface is needed - the Arduino can drive an LCD screen directly. There are input modules for the BS with everything from a sonar ranging circuit, to GPS, to fluxgate compass, and even gas sensors. They are the equivalent of modern-day Erector sets. The Pi is a great device, and I don't want to minimize its importance, but until you can easily hook up a breadboard with buzzers and lights, it's just another video game.