ThinkGeek has launched a product page for its upcoming TK-421 iPhone Case with Flip-Out Keyboard. Available in separate versions for the iPhone 4 and iPhone 3GS, the TK-421 boasts a flip-out physical Bluetooth keyboard with a magnetic clasp that keeps it in position whether opened or closed and a built-in rechargeable battery that charges over USB, as well as a two-piece design and open access to all ports and controls; it is unclear whether the caseā¦