I am all for letting kids display independence at a young age.
The summer before she turned 8, I allowed DD to go to her friends' houses in our small neighborhood, and to play in the open field behind our house. I had purchased a set of walkie talkies, and if she needed me, she could use them.
Once the summer was over and she proved that she could be trusted within the allowed areas, I gave her free reign throughout our small neighborhood (3 main streets with several culdesacs branching off). She could come and go as long as she informed me where she was going first.
When she started 4th grade, I was confident enough to let her cross the busy road in front of our neighborhood and walk to school (less than 1/4 mile away) and to the park behind it. Some other moms in our neighborhood thought I was too permissive, but I knew DD was responsible.
When she was 15, we sent her off to boarding school 150 miles away. It was a great accomplishment to be selected to go, and she was excited for the new challenge. We raised her to be independent, and she has become an accomplished, fearless young lady.