We have recently added webhooks to our API. Now you can configure webhooks such that every time an activity takes place involving a lead, an HTTP POST request can be sent to a URL or multiple URLs of your choice. 

There are 33 types of activities in total that are tracked. This allows you to get real time notifications of activities, such as a lead being marked as won or moved from one stage or another. The full list of activities and the webhooks documentation can be viewed at the webhooks API documentation page.

You can add webhook URLs by going to see your Settings page and then selecting Integrations. You’ll see a Manage Integrations link for Webhooks on the integrations page.