Is there a pocket pc which requires only one hand to hold and
operate, with a keyboard for the thumb? <<

I think Captain Kirk had one that allowed him to maintain his captain's
logs in addition to processing complex computer needs using voice only ;-)

Seriously, time to look at what's available, justify the price and see
what it's capable of rather than requiring your specs to be met in
advance.... you have gotten a lot of good suggestions, so it's up to you
to decide yes or no and either reap or refuse the benefits that are
currently there for the taking.

Thumb keyboards are available, but no current built in or snapon
keyboard is going to offer you onehanded operation.

Beverly Howard [MS MVP-Mobile Devices]