Hello, I would really like to participate in your project. I have more than 15 years of experience developing software, the last 10 on c#. I am an expert in web services, and I also hold a degree on Computer Sciences, so the calculations won't be an issue.
I think a latitude - longitude input would be better for you, since you can then add another calculations by adding a conversion from.
Just to confirm I am understanding that the calculation is the distance straight-line, not a calculation of a route through viable roads.
Please let me know if you are interested.