I know a handheld might not be the perfect device for programming, but for me it would be useful for working in short periods of time, for example while traveling, so please don't make it a debate about if it's a good idea or not.
According to what I've been looking, the device must fulfill the following characteristics:
- Keyboard: Full QWERTY (including symbols). It should be not bigger than 6", or be divided in two parts (like this) and should have the buttons sticking out for easy use.
- Connectivity: Wifi would be ok, but mobile connection would be better yet.
- Performance: Should be enough to explore modern internet websites.
There's just one that actually fulfills all characteristics, but is still just a project, and very expensive by the way: the DragonBox Pyra, the unique problem (ignoring the price) is that it's ARM based.
Other great option would have been the "Pepper Pad" but lacks in performance (and are not produced anymore), other one would have been the "Sony VAIO UX", but people says the keyboard is difficult to use, so it lacks too.
Sorry for not posting links to all devices, I can't as I don't have reputation yet.