Since average speed has to do with "motion", I fail to see the relevance of including "stop time" when doing a calculation involving "average speed". This would kind of be like telling your boss that you worked an extra two hours and when he/she asked you what you did in those two extra hours you tell him/her that you had two hours of coffee breaks.

Regardless, your android has a calculator. Take the total mileage of the route and divide by the total time of your choice ( in hours ) and you have your answer in MPH. ( Not that it will mean anything if you include the time you lollygag around but hey, whatever makes your day FWIW ).