BT has had an advert banned by the ASA that was trying to promote the interference avoiding abilities of its dual-band Home Hub, with the advert featuring on screen images of various devices with the implication that these types of things could cause Wi-Fi interference.
Three complaints were made about the advert, and the ASA banned the advert on the basis that a mobile phone and private mobile radio devices (walkie talkies?) whose images featured had not been found to be causes of Wi-Fi interference.
The reality in the real world is that while other devices such as baby monitors and video senders also use the 2.4GHz spectrum, the biggest issue in 2013 is likely to be overlapping wireless networks from other router. Hence the increasing popularity of wireless hardware that can use the less congested 5GHz band.
Wi-Fi has been a key driver behind the tablet revolution (or is it an addiction), but even in areas where there is no interference, Wi-Fi cannot beat the reliability of a wired (Ethernet) connection, hence why we suggest in our speed test that you use an Ethernet connection when testing your connection. Generally wireless congestion shows up as unexplained drops in speed during a test, or our tbbx1 test showing a variable speed with the httpx6 running faster but still slightly variable. This is why we display the graphs from a speed test, rather than just the average speed, which can mask congestion and wireless issues.