Back in January, ATT and Asus announced that the PadFone X, the latest version of Asus convertible smartphone and tablet concept, would finally come to the US this year. The PadFone X will sell for $199.99 with a new contract and comes with a docking station that converts the 5-inch smartphone into a 9-inch tablet. Asus has been pushing its PadFone concept for years with a variety of designs that all play off the turn your smartphone into a tablet and back mantra. Asus isnt exactly known for its smartphones in the US, so it will likely be a challenge to get customers on board with its unique vision for what a smartphone and tablet should be.