Since K-On ended up becoming a phenomenon since the first season's release, there's already more merch for it than I can even remember, but this recent one caught my eye and ended up being one of the moments when I wish I knew how to speak Japanese even though there was already an introduction to it on this very site. There's this article for the themed Portable GPS that showed up on ANN not too long ago and judging from it as well as the original source (it's only in Japanese, but sadly, my chrome browser couldn't pick up any text from it, so I had it translated in order to actually read it).
It looks like a cassette tape when being started up, but it then goes to a themed menu, which also includes the settings for which band member to pick. The voices of Yui, Mugi, Mio, Ritsu and Azusa can guide the user to their destination when one of them is chosen as the avatar for your car.
It just got released in Japan, so it looks like the fun begins for the lucky bastards who come across this. I doubt this'll end up with an English version option, but a guy can dream, can't he?