Yes, this is the automobile speedometer we all know and love. Tesla invented and patented this in a desperate attempt to get some cash flow during this incredibly difficult period of his life. Note that it was during World War I — his home country of Serbia was deeply involved in that conflict. From 1907 on, Tesla had been almost totally broke thanks to a few manipulations by former backer JP Morgan. So during and shortly after the war Tesla concentrated on a few inventions that he hoped would make some money. They didn't make much, but it helped. Still, he wasn't able to keep the great Wardenclyffe tower from being torn down in 1917.