Wireless sensor networks typically use a border router to bridge the WSN to the Internet. Often border routers are also embedded devices that connect via USB to a computer. They have wall power, but have the same computational and memory constraints as the WSN nodes do. The connection to an external computer also makes them hard to deploy. To relieve this, I built a CC2520 based daughter board for the Raspberry Pi platform. This creates a computationally competent, small, easily deployable device that is ideal for being a border router.
My testing setup: