Let's get this out of the way: the Logitech Joystick ("for iPad and Android Tablets") is a strange little gadget, an analog solution to a digital problem. It sticks onto your tablet with suction cups, then places a capacitive touch-point below a thumbstick modeled after the more recent generation of game console controllers. Motion is achieved via a coiled plastic spring, and its design allows you to move it around the bezel to adjust to different games. The list price is $20, but right now Tiger Direct has it for free... after a $9.99 mail-in rebate.
The Joystick has been on the market for about a year.