My favorite notepad is simply a 8.5" x 11" piece of cheap copy paper folded in half. Every time I buy a sketchpad or notebook the paper is too grainy for my taste.
Sometimes i'll fold the paper a second time to fit in my pocket, but I draw on it folded once. With it completely unfolded the paper is too flimsy and the canvas is too big but with it folded once it is just right.
Try this method with the previously mentioned pens/pencil and you'll crank out some art.
Sorry for veering off topic, I'd ask Rimrook about the apps.
@Tet, i'll have to try the gel version, I was always curious about it.
@Captain, looks cool what is it? You should consider industrial design.