Accessing Posts externally through HTTP

Hi, I am developing a .NET app for Windows and I want to retrieve today’s post from my WP site. Does WP have an externally-facing API I can use? I do a daily post to my WP site and after it’s published, I want to click a button in my app which retrieves the contents of the post (including anything inside http comments).

So if I could do a HTTP POST and get the latest post returned, that would be simple and ideal for my purposes.

Thanks.