"A WiFi camera, operating on channel 1, is streaming video. When I switch on an analogue, wireless babycam, you see a strong signal appearing near channel 9 (watch the SPECTRAL VIEW of the Wi-Spy spectrum analyzer, e.g. the window in the upper-left corner). After some time, I switch the babycam to a channel near channel 1 of the WiFi camera. Now the transmission of the babycam jams the transmission of the WiFi camera, and we lose connectivity.
Powering off the babycam restores the WiFi connection."
The blog entry includes a link to a video demonstrating the attack, illustrating the danger and ease of a layer 1 attacks.