The Xperia Play has yet to be challenged by another device with a gamepad. It is a pretty nice feature, and an accessory from Gametel allows you to connect the device to your phone or tablet via Bluetooth.
The Gametel Bluetooth controller attaches to almost any android device (below about 4.7 inches screen size), but as it uses bluetooth, it can be used whilst detached from a device. You could link your phone or tablet to a TV and play from the other side of the room.
The device has actually been out for a while in the UK (and some of Europe), and can be brought from Amazon for £50. A US release is currently being planned.
If you like to gaming on your tablet and/or phone, this could be a perfect accessory for you.