Sosius
a.k.a. Uptown Frunk
So far all I see is Marketwatch promising a live blog here. Of course it will be stupid because it's Marketwatch, but better than nothing.
Transportevolved.com will also be liveblogging: Breaking: Tesla Motors to Make Surprise Webcast Today at 18:00 UTC, 11AM PDT Is This the Model X? | Transport Evolved