Here's a great idea for attaching a tiny pan of watercolours to your sketchbook:http://freekhand.blogspot.com.au/2011/06/going-hi-tech.html
How do you use your sketchbooks (or are they journals?) Here's one way: http://josephstoddard.blogspot.com.au/2012/02/finishing-previous-sketchbook.html Joseph Stoddard keeps each sketchbook intact and says he only does one per year. He goes back and finishes sketches that he didn't finish onsite, and pastes in the photos he took at the site. My approach is that I have probably 5 or 6 active sketchbooks at any time, and when one is full I sometimes rip out pages and file them along with other sketches and photos of the same subject.