Plancast — a service that lets you share future plans with friends, and view those from others — just got a whole lot more useful today. The company announced its API (application programming interface), which gives developers the ability to use Plancast’s data in their apps, reports the technology blog TechCrunch.

The service is best described as “Foursquare for the future.” Instead of telling people where you are, you can broadcast what you’re going to be doing at any given point in the future. It’s similar to a shared calendar, except it offers up a social graph like Twitter or Foursquare. You have the ability to follow people you’re interested in, and you can also lock down your profile to select readers. Not surprisingly, Plancast is looking to integrate with calendar services like Google Calendar. It also recently added the option to import events from Facebook.

Now with the addition of an API that’s read and write-enabled, developers will be able to build applications that both read and send data to Plancast. Exygy, a third-party developer, is already using its API to develop an Android Plancast app called Plandroid.

The company is also unveiling widgets that will allow users to easily show off their plans on their own websites. Currently, there’s a small sidebar widget, as well as a full-page widget for those who want to dedicate a page on their site to future plans. As is usually the case, with widgets also come buttons, which allow users to link directly to their plans.

Based in San Francisco, Calif., Plancast recently landed $800,000 in seed funding from several investors.