Eric Enge over at SEW wrote in his post "The Challenge of Mobile Analytics" about different vendors and their technology: "Packet sniffing. This approach relies on installing an additional server (the "mobile analytics server") into your Web environment. A switch is then used to pass a copy of the incoming packet data to the mobile analytics data, while allowing the same packets to pass through to the mobile Web server without any delay. In addition to basic Web data, you can get information on handset resolution, the mobile operator, handset type, and browser type. Australian based Amethon uses this approach.
Site redirection. This method relies on traffic being redirected through a different server, and then redirected back to the mobile Web server. This also allows for the collection of a rich set of analytics data, similar to what you get with packet sniffing. This approach is used by Bango."
Really great post. I've talked to some mobile engineers and there is still a lot of research necessary, especially that new devices come out every week.