I was searching for alternative keyboards (my keyword for that was "word processor") in order to make my writing work efficiently. I found some really good portable word processor in terms of battery life.  They were from 50 to 700 hours with using three to four AAA batteries. I saw a Youtube video telling that a teacher used the device without changing batteries over a year.

Some of the links of the products are:
http://writerlearning.com/
http://www.renlearn.com/neo/NEO2/default.aspx
http://www.neo-direct.com/default.aspx
http://www.quickpad.com/Index.asp

Among the above, currently, the most cost effective tool seems AlphaSmart 3000.  You can purchase a used one at Ebay under $50.  The new one is called NEO, which is around $169, currently (see the above YouTube video).  Since Amazon Kindle does not provide an annotation function for pdf files, using NEO(AlphaSmart 3000) seems the best solution for that use.

I find myself to get easily distracted when I am online. So, using one of the above might make myself more focused.

The authors on the following link reviewed different types of keyboards and input devices very throughly.
http://www.aiu3.net/uploadedFiles/Curriculum_Instruction_and_Professiona...