What Is It ?
A Raspberry Pi is essentially a small computer, the size of a pack of playing cards. It has a microprocessor (ARM 700 MHz), 512 MB of RAM, 4 USB ports, and an Ethernet adapter... and it can run Linux. That means that any USB stuff that works on Linux should work here, e.g. wifi adapters, packet radio adapters, even a GSM adapter for cell service. Even better -- it has a bank of GPIO and I2C slots so you can plug in physical inputs and outputs such as temperature sensors, motors and relays, motion sensors, cameras, LEDs, LCD readouts, touchscreens, and serial I/O such as GPSs. And it all runs off a USB phone charger, and doesn't even have a fan to make noise.
More info here: http://www.raspberrypi.org/products/model-b-plus/
The whole concept of the Raspberry Pi is a dirt-cheap prototyping platform. Remember those electronics kits we had as kids, where you wire up resistors to antennas and make a crystal radio? Same idea, except one of the components is a Linux computer connected to the Internet. And that computer has 26 software-controlled input and output ports.
And of course, there's a real thrill and "tee-hee" value to a working computer that's the size of a hamburger patty, which runs X Window and a SMTP server and a MySQL server, and just about anything else that runs under Debian Linux.
Anyway, it's not really map related at all but is some cool stuff. In upcoming weeks, expect a few raspi postings mingled in with my usual map postings and my (overdue) series on choosing a HTML5 framework for mobile dev.