Perhaps he means the London Visitor Travelcard which is a 3/4/7 day product that you can buy only from US or Canadian travel agencies, good for all 6 zones of travel at all hours on (almost) all public transport types within London (you can not use it on the Heathrow Express). I always buy them, even though they aren't comparatively economical right now with the current exchange rate. But they are sure convenient. You change the ticket stock for the pass at LHR and then just hop on the tube.