I would like to use of Chatter API to enable the "Follow" capability on assets in an external (to force.com) system. In other words, we have a website/application that has assets which we are interested in enabling our sales team to "Follow" so that updates to those assets are posted to their Chatter feed in our salesforce.com installation.  We want to put a "Follow" button on one of our non-Force.com hosted sites so it can post updates to Chatter in our salesforce.com installation.

Here's an example scenario:

Sally Salesperson finds KillerApp: A Sales Presentation in our site (a non salesforce.com hosted web application) and decides she wants to know about any updates to the document, so she clicks the Chatter "Follow" button next to it.  This posts a quick chatter status to Sally Salespersons Chatter feed indicating "Sally Salesperson is now following KillerApp: A Sales Presentation" (and "KillerApp: A Sales Presentation" has a hyperlink back to that resource on our site).  Sometime later KillerApp: A Sales Presentation is updated on our site (say a new revision is uploaded), at which time Sally Salesperson's Chatter feed is updated with something like "KillerApp: A Sales Presentation has been revised." (again, the document title is a hyperlink). If Sally Salesperson then downloads the updated presentation, a Chatter update like "Sally Salesperson downloaded KillerApp: A Sales Presentation" would be posted.

I've been told by salesforce.com online chat support that this is not currently possible and that I should put this idea out here. Does anyone else have this use case?  Anyone have ideas as to how this could be implemented currently?