Jot script. It's .5 tip is great for iPad. I use it with myscript notes. Your hand writting can be cursive and searchable. You can also OCR convert a written text.
Learning curve is 1 - 2 weeks.
Battery life is about 4 hours. So i have about 2 extra AAA rechargeable batteries handy. The short battery life or absence of built in rechargeable is small trade-off to utility & function.
I tried a couple of others, my search ended with this pen