I have never thought of this, as I have a pedometer and don't need step substitutes. The thing is, a lot has to do with your stride too. If you and I walked the same 1/2 mile, one of us would have more steps, because one of us would have a smaller stride, so it would take more steps to reach the destination.
You can buy inexpensive pedometers for around $20 and they work just as well as the more expensive ones - just without all the bells and whistles. I got mine for free. It's old and big and ugly, but it works. I keep it on me all day long to track my steps.
I hope this helps you somewhat.
| current weight: 143.4