In case you missed the late 2012/early 2013 console release of Sonic & All-Stars Racing Transformed, Digital Sumo has just released the game's mobile port for iOS and Android (it's also worth stating that the game's home release was arguably one of the best mascot kart racers in years).
Also of note: the mobile version includes Shenmue's Ryo Hazuki as a playable racer, riding various arcade cabinets (Hang-On, Space Harrier, etc) that change depending on whether he's racing on land, sea or air (though Ryo is conspiculously absent from the trailer, for some reason). As per the game's predecessor, Transformed is a loving tribute for Sega fans new and old, and given the significant boost in processing power for mobile titles, it actually looks pretty slick. Now if Sega would just go back to making decent Sonic platformers...
Sonic & All-Stars Racing Transformed will run you $5.