the nissan bit i mentioned was around 5-6ish year ago.. i know toyota had heated screens fitted to cars in the 80s so presume before the ford patent you talk of expired. in regards to bmw the only defoggeras you put it, that i have come across is in the form of a moisture sensor behind the interior mirror cowelling..when it senses moisture it auto put the heaters on to the windscreen..only recall them using that from around the time the e90 was introduced though i stand to be corrected