One for @Joby I remember this episode of Tomorrows World and thinking who would ever want such a device!
As it happens back in the late 1970’s I chauffeured wealthy Americans and their families around the sites of London. We had no such gizmos in our stretch Granny’s and managed to faultlessly navigate by the very comprehensive Geographers London Street Atlas supplemented by candle light after dark. I don’t know how many of those Americans believed me when I told them “Yes, there are two Nelson’s columns in London” ;-(