Just got my new Logitech keyboard. Designed for Android 3.0, not iOS or WebOS, but it works great. Its a separate keyboard, but has a built in case for the keyboard which converts into a cradle for the Touchpad. You can use it even while in the stock HP Touchpad folio case.
Logitech® Tablet Keyboard for Android
So far its working great. I haven't found any keys that map to the card button yet, but I really only wanted it for text entry during meetings. Found it for $59.99 up on buy.com, but I"m sure we'll see deals soon bringing the price down in places.
Buy.com - Logitech Bluetooth Wireless Keyboard and Stand Combo for Android 3.0+
Case is kind of cheap, just plastic, but the keyboard is flat out awesome.