Collaboration company 37Signals bought the popular Ember iPhone app, which uses the company's Campfire API (our Campfire API profile) to display and update chats. The app has been renamed 37Signals Campfire and is now available for free (previously $9.99).
Lately we're seeing a lot more talk about API monetization. Last week we covered TweetPhoto's efforts at encouraging developers to use the TweetPhoto API through a transactional payment model (one penny or so for each photo uploaded via the API). Last month we covered Bandsintown, which provides affiliate earnings via use of its Bandsintown API. And more recently Touchnote announced an affiliate payment model (with a whopping 30% royalty) for developers working with its image API.