Monday morning I spent a few minutes chasing down links and reading a few concept papers. Pretty cool stuff. Here is an article by Steven Letendre and Willet Kempton that appeared in Public Utilities Fortnightly in 2002: “The V2G Concept: A New Model for Power?” (pdf).
The high value usages are in supplying a variety of high value power products like automatic generation control, responsive reserves, reactive power and real power supplies during system peaks.
Practical home applications involving resale to the local grid are probably a decade away, at least. (Maybe I’m wrong. Call your local utility and ask them how they feel about the idea.) I’d expect emergency home power replacement applications would come about much sooner.