Embeddable Enterprise Collaboration (Microblogging) Engine

Short Version (tl;dr):

Is there an open source or commercial engine that provides embeddable collaboration and microblogging functionality?

Long Version:

I am creating a niche application that has need of this functionality and do not want to reinvent the wheel. The following are must have requirements:

• Data API only. My application is SaaS, and I want to build the functionality around the data. This eliminates most of the offerings out there (facebook, salesforce chatter, yammer, present.ly, teambox)
• Does not require use of a built-in front end. I really just want an engine that will take care of the storage and events, and gives me a means of querying. Requiring the use of a specific front end renders it useless for embedding into my app. This eliminates everything else I have found (status.net, Yonkly, Jaiku)
• Beyond standard updates and replies, can handle custom events. For example, if I were embedding this into an logistics application, I could have the engine handle events like "shipped", "received", and "cancelled".

Beyond this, there are several nice to have features that a framework would have:

• Should not require a specific platform or server technology to run (i.e. something like a RESTful API would be nice)
• Should be message based so that commands that affect its state can come from any source
• Should encapsulate its own storage so that external resources are not necessary (i.e. no database needed)
• Should have pluggable extendable UI components/widgets for web, mobile, and desktop clients
• Should have search and retrieval APIs available for many languages/platforms

It seems that someone out there should have this already, or at least be in progress with it. Please point me in the right direction.

Since nobody had any answers and continued research did not find anything, I created a solution on my own called Collabinate. Updates can be found on Twitter, and the project itself is hosted on GitHub.