If you own a tablet, you probably own an iPad, and it's a very convenient tool for some quick writing. Editing, though, is less pleasurable, in my experience.
Jason talks about Evernote in his introduction. I use this too, and it's a very usefull cross-platform note-taking system.
Initial ideas, whether I'm at home or out and about, get tapped into the Evernote app on the iPhone, where they are then synced across the ether, ready to be examined on the PC at a later stage. I used to do this in a physical notebook, but I find that it's all too easy for scribbled ideas to become lost among those pages. With something like Evernote, you can organise ideas into different notebooks ('Doctor Who ideas', 'short story ideas', 'feature ideas', etc) and easily assess them all in one place when you're looking for something to work up, or an idea to cannibalise.
For developing ideas, Jason points us at three iPad writing apps in this article, Pages, IA Writer and OMMWRITER. Each has their pros and cons (that's what reviews are for).
I've also used the Index Card app to do some storyboarding work on my iPad. It's a nifty app, not very expensive, and great for tapping out scenes and moving them around to get a feel for your narrative flow. It exports to Scrivener, too, if that's your thing.
Anyway, check out Jason's review below: http://jasonarnopp.blogspot.com/2011/10/three-good-writing-apps-for-ipad.html