It looks to me from the not massively clear photo like a metal ring with lots of fine wires inside it. So it's intrinsically a heat diffuser, regardless of any magic catalysis action. But they're for sale on an awful lot of eco-stores. One claims a typical gas saving of 12%. This one (http://www.ethicalsuperstore.com/products/good-ideas/gas-energy-saver/) claims that the manufacturer quotes "an average 14% reduction in heating time based on heating 500ml of water from 18.5 degrees centigrade to 100 degrees centigrade using a medium sized (1.5 litre) saucepan on the small burner of a four burner gas hob."

Amazon's reviewers agree with your results, however: http://www.amazon.co.uk/SET-SAVING-ENERGY-NETS-IMPROVED/dp/B001E9UZCO

Perhaps you should call the ASA or Trading Standards?