One of the best motivators for me during a walk/run, is having apps that let me know how well I am doing, mileage wise, and in turn, calorie burning. One of the apps I use is Runkeeper This app allows me to set the type of workout I am going to follow, and it will keep track of mileage, and calories burned. You can set your goals, and watch yourself improve. I use the basic version as I need to upgrade my phone, but given the opportunity, I will upgrade.
Another app/equipment is the Fitbit -
This is the absolutely best little gadget I have ever used - this can be set up to work with many other apps such as Weightwatchers, and the Runkeeper app as well.