How accurate GPS with distance walked?

Unfortunately, RunKeeper beat you to it ... http://itunes.apple.com/us/app/runkeeper/id300235330?mt=8

I use the app nearly everyday. GPS works perfectly.

GPS accuracy is, at best, within about 20ft so there will always be some variance over long distances.

This is due to a restriction placed on the GPS satellites by the US Government

FYI:

By order of the President of the United States, the use of Selective Availability was discontinued on May 1, 2000.

Before Selective Availability was discontinued, accuracy was somewhere in the 30m range, now it's only about 5-6m

Consumer grade GPS devices are only accurate to 10 meters or better, 95% of the time without WAAS and that will improve to about 5 meters with WAAS(Wide Area Augmentation System).

Simply a limitation of consumer grade GPS's units. There are no restrictions imposed by the US government.

Here's some good info:

http://www.gps.gov/systems/gps/performance/accuracy/

Then why did you post this in your initial response, which is inaccurate?

"This is due to a restriction placed on the GPS satellites by the US Government"

I'm not arguing with your statements. I was incorrect and you had more up-to-date information than I did, but I have followed up with good references for the OP to look at and my first sentence was correct "GPS accuracy is, at best, within about 20ft so there will always be some variance over long distances".

I'm not sure why yoou felt the need to argue with my US Government comment three times. I read it the first time and didn't dispute it.

You don't work for them do you? 😉

So that if I take 2 two steps forward an event is triggered in my app..

Using the iPhone's GPS, my experience tells me it would be highly unreliable trying register only 2 steps. 10 steps maybe, but not 2. And that's outside... it would be worse inside.