Phil Windley has written about using Foursquare data inside SquareTag. Foursquare uses push notifications that look like Webhooks and thus can be used to raise events. 

• Foursquare and Personal Data in a Personal Event Network
• On Call TA: Distributed Event Network Federation Through Subscription

These examples are a little dated from a terminology standpoint, but the concepts are still valid. The following were all updated or changed years ago, but need to be updated again:

• CloudOS and it's PDS service didn't exist at the time these experiments were done, so the PDS referenced is a prototype and some functions have changed. 
• SquareTag didn't exist, so the example uses the Kynetx Browser Extension to manage applications. 
• The TA network relies on hand-coded subscriptions, but the Forever application could be used to manage those now. 
• The TA example also shows how Twilio SMS messages can be used within a SquareTag application.