There are lots of Wi-Fi buses popping up in Northern California. The Google shuttle from San Francisco to the Valley has been running for a while and I think Yahoo! has a similar service, but I saw this Wi-Fi enabled AC Transit bus (that's Alameda County folks) crossing the Dumbarton Bridge last week. Apparently, the service is being subsidized by a grant from the Alameda County Congestion Management Agency.
I strongly believe that these kinds of amenities are the things that transit needs to be competitive in the US. But I also worry of their potential to push the commuter shed for big metropolitan areas out even further than they already are. In the New York area, we're already seeing daily commuters from northeastern Pennsylvania - up to 2 hours away. I suspect that Blackberries are a huge part of making that bus ride (and buses are the only option) bearable and productive. In Northern California, one of my colleagues makes a similar trip from Tracy to Palo Alto on a wireless-ready commuter train. (though ironically the San Francisco-San Jose CalTrain, filled with digerati every morning, recently abandoned plans to put Wi-Fi on its trains).
The potential here is great - but connected transit will need to be tied to transit villages and compact land use strategies to achieve its greatest congestion-reducing, space-preserving, walkability-enhancing impact.