The Interceptor
The Interceptor is a wireless wired network tap. Basically, a network tap is a way to listen in to network traffic as it flows past. I haven’t done extensive research but all the ones I found when looking passed the copy of the traffic onto a specified wired interface which was then plugged into a machine to allow a user to monitor the traffic. The problem with this is that you have to be able to route the data from that wired port to your monitoring machine either through a direct cable or through an existing network. The direct cable method means your monitor has to be near by the location you want to tap, the network routing means you have to somehow encapsulate the data to get it across the network without it being affected on route.
The Interceptor does away with the wired monitor port and instead spits out the traffic over wireless meaning the listener can be anywhere they can make a wireless connection to the device. As the data is encrypted (actually, double encrypted, see how it works) the person placing the tap doesn’t have to worry about unauthorized users seeing the traffic.
Read more http://www.digininja.org/interceptor/