I will go with thumbboard it seems that is used but Wikipedia too. There are more types and styles of these than there are names for them.
I have been using this form of typing since 1998 when Nokia released their 9110 Communicator and have got very accustomed to it, I actually prefer it to so called regular keyboards now.
So what am I looking to say about these keyboard types? Well it has bothered me for the longest time that they have got such a poor reputation by many. This however in my opinion is because the vast majority of gadgets out there that use thumbboards have a very poorly designed thumbboard. So what is a poorly, or rather what is a good design for a thumbboard? Well I will cover here what my decade of using thumbboards have led me to believe a great thumbboard should have.
First off it is my firm belief that a good thumbboard needs to have at least five rows of keys. The sad fact is that many have as little as three rows, and I'd believe it is safe to say that the majority at this point have no more than four rows. Why is this important? Well for the simple fact that you will need to press a combination of keys to get various symbols and numbers a lot more when you have less rows of keys. The more dedicated keys you have the better it is to use, this will mean more rows. If you are on a desktop, laptop or even netbook when reading this, just take a look at your keyboard and count the rows from top to bottom. Without the F or other special keys you most likely come to five. This then ties into the next subject, space. Many will claim that if you want that many rows it will take too much space. Not necessarily.
Secondly space for the keys. It is a common misconception that the keys on a thumbboard have to be relatively big in order to be better. Many even use this in their sales pitch. But is this true? Do the keys on a thumbboard need to be big? Let's look a bit closer at this. Some time ago Apple came out with a new designed keyboard, it used relatively low flat and what seemed to be a lot of space between the keys. Since then others have followed. Now was this something very radically new? Not really if you have a "traditional keyboard" close by, look closely at it. The keys are yes next to each other or just about "touching" on a traditional keyboard, but if you look at the top surface of the keys (the are your fingertips actually touch) you might notice that they are not as close to each other after all. Most keys on traditional keyboards have a certain amount of pyramidal design to them. So why this elaborate explanation about keys? In a similar fashion you do not need large keys on a thumbboard, nor do they have to be "side-to-side" in fact it is better if they are not. It is surprising how well one can type on pretty small keys, if they have decent spacing and not all to sharp top. The spacing gives better ability to learn where the keys are and being able to find them without actually looking at the keys, as you start to orientate by touch.
Thirdly layout, the keys should be in a similar fashion as they would on a regular Qwerty keyboard since while not typing with the same fingers it is easier and thereby faster when you don't have to learn new locations for the symbol you need.
Fourthly soft or hard? Both have their pros and cons. With most softer keys they tend to wear out in some form or fashion, while being easy on the thumbs. The harder keys while having a better longevity tend to take a toll on your thumbs.
Last but not least this kind of ties into maybe both layout and spacing, the overall width of the thumbboard should be wide enough to not be cramped. Personally I find all of the bar style smart phones with Qwerty thumbboards to be too narrow. At the same time they should not be too wide, the Nokia Communicators mentioned at the beginning are on the borderline of too wide for me personally. Personally I have not yet found any thumbboard that I feel as comfortable typing on as the Danger Hiptop / T-Mobile Sidekick.
With a good thumbboard and being interactive and multitasking one can become pretty efficient and comfortable on these types of keyboards. While I do also use an iPhone as a second device and do occasional tying inputs on the onscreen keyboard, I consider that as a two hand-two eyes procedure. Whereas on the Sidekicks I have got to the point where most of my input can be done without looking, including with one hand/thumb at times when the occasion requires that.
