The PKB-800 is apparently the world’s first Universal PDA Thumboard. Works via infrared too, so take that you Bluetooth ninnies.

‘PKB-800 works with most Palm OS3.5 to 5.2 ,Pocket PC 2000 , 2002 & 2003 PDAs…Measuring in at a mere 129�90�18mm , It is small enough that users can use all 69 keys and complete functions with Only [sic] their thumbs…’