Writes Mossberg (WSJ):
The SpeedStream gadgets create a parallel, wired network in your home using the electrical wiring, and then turn it into a wireless network. The SpeedStream products are really meant for building a so-called Powerline network, which is a wired competitor to Wi-Fi wireless networks. But Powerline networks have struggled to gain acceptance in the face of Wi-Fi’s popularity, so Siemens has cleverly merged the two types of networks by building a Wi-Fi transmitter onto a Powerline wall adapter.
These SpeedStream Powerline products are made by a company called Efficient Networks, owned by German conglomerate Siemens. The Powerline Wireless Access Point costs $99 and the Powerline Ethernet Adapter costs $89.