There are apps and.
Many apps exist that you can monitor your progress, both for iphones or android
) devices, which have gps.
I am not endorsing a specific app, but with my iphone 4s, I use an app called cylcemeter, which measures and maps my routesw on my mountain bike, calculates speed, and if i redo the path later, it will compute your average speed for both. Many apps are available. See what the reviews are.