The Boston Freedom Trail is quite easy to walk. You don't need an esoteric GPS navigation. You simply follow the line on the ground, and the Freedom Trail Plaques along the way.
It is literally like following the Yellow Brick Road from the Wizard of Oz. A golden ribbon leads you from place to place, and you move along it. You also get these beautiful plaques to keep you on route.
The plaque says "Boston The Freedom Trail" and has leaves around it.
Boston Freedom Trail Main Page