OK... so I'm posting before I have had a chance to read the spec sheet, as I don't have the time at the moment... But...
Surely these would use an I2C or a SPI interface to be programmed? I thought the PFC8544 driver used the same interface? Wouldn't it be theoretically possible to modify that driver to program these?
Also... If it is I2C or some similar serial method of programming, it would be also theoretically possible to have multiple keys connected on the same bus. Therefor making it possible also to map out a number of keys. LCDinfo could be made to do this by programming the driver to take into account the multiple screen addresses and mapping those to area's of a bigger screen. ie; If each button is 20x15 pixels, and you want to use 4 buttons, then you ave a display that is 40x30, or 80x15, or even 20x60 pixels. Sure, this could lead to some strange pictures on the buttons if somone uses bitmaps or text larger than the button size, as it would cascade over to the next button, or just not fit in the display...
Hmmmm Schlepp.. I like your thinking, they would be great toys.

Even if LCDinfo doesn't support the button inputs, the buttons could be used via another input, or even externally, and the information collected via a plugin.
Anyway.... I've said my piece.

Just thought I would start more of a conversation.. or not.

After all, the idea of these forums is to share information, and discuss idea's... isn't it?
Lots to look into...