As for the historical markers in Virginia, Tom Scheinfeldt wrote in his comment:
In fact, we at the Center for History and New Media are working to launch a project called Virginia History Here, which will use new mobile communications technologies—especially cell phones—to improve access to Virginia's historical roadside markers. In addition to providing searchable web access to the markers, Virginia History Here will allow travelers on congested roads to access the full text of historical markers from within their cars via cellphone. Moreover, in order to help extend the historical and educational value of cast iron markers, Virginia History here will also provide these travelers and web visitors with links and directions to nearby and related markers, contextual essays, and related primary source materials such as photos and short audio and video clips. New mobile technologies allow us to make all of these resources available to travelers when they are most interested and engaged: when they are at the marker sites themselves.The Virginia project sounds very interesting! I hope it gets funded.
We are still waiting to hear about funding, but if all goes well, we should launch a prototype by 2008.