Hi Andrew, there are a couple different ways to accomplish this, and it mostly depends on the system you’re integrating with. For starters, you might want to check out our webhook:

http://support.unbounce.com/entries/3…

Can you describe your situation a little more? What sort of API request do you want to make when you get a form submission?

We are looking to use an API XML submission method that when there is success on our end then it will trigger a message to the user.