Oh my gosh I can't believe all the responses I got. Thank you all so much! I am going to try the GPS from my car. And if that doesn't work, I now know many apps I can use from my new Smart Phone!

I have a speedometer. It serves two purposes. One it tells me how fast I'm going, but more importantly, I reset the odometer every morning so I know how many miles I've traveled that day.

Speed Box on the iphone works great for this purpose.

Go to apps and search for speedometer. There should be several free apps that will tell you how fast you are going.