DIY enthusiasts make their own cell phone tower using a Raspberry Pi

You've heard of the Raspberry Pi, haven't you? In case you aren't familiar with the cool, little gadget, it is a dirt-cheap Linux computer popular among DIY enthusiasts. Since it costs only $25, many engineering projects revolve around it, including this one for a cellular phone tower made by PA Consulting in the U.K.
So yeah, this Raspberry Pi based project is a great demonstration of how expensive cellular infrastructure can be substituted to some extent using cheap, readily available hardware. Imagine a low-power emergency phone network made using a bunch of these, or how infrastructure expansion costs could be reduced with the help of identically affordable computer modules.