I use FRAPS. It's free (with watermark), or pay $40 once for a lifetime license per person (i have actually been refunded the cost of a license for additional machines in the past - they are good people)

I do accurate-ish line drawrings with stick figures on a white pad in purple ink, then I take iPhone video of the flip-pad movie

I also use fraps and highly recommend it. I bought it back when it was $28, it is still worth getting now at $40 or whatever it currently is because you get updates for life and it's as simple as logging in

and downloading your update