Exactly! I still use business cards, but I print a QR code on the back that can be scanned by a smartphone. The Droid will read it and add it to contacts, including name, address, email, phone, etc. I think a QR code can contain up to 4K of text?

Why not just get something like the Logitech DiNovo Mini? Its a bluetooth keyboard/trackpad combo that fits in the palm of your hand. Logitech only supports it on Windows, but its recognized on the Mac and should work as a keyboard/mouse on Linux as well. I've not tried it with Linux as none of my boxes have bluetooth...

Sounds to me like what you want is a modern-day Newton priced like the iPod Touch!

You might look at Snake Wrangling for Kids or perhaps at How to Think Like a Computer Scientist.