I received a direct message on twitter from @GiftedTawk with the image to the left attached. She was wondering if there was a way to create this effect on iPads.
The image and the challenge inspired me, so I pulled out my iPad and got to work.
I took a photo of myself as if I was drawing myself and put it in Adobe Illustrator Draw to create a contour line drawing with the black ink tool. Learn about contour line drawing from Grandpa Pencil here. Then I layered both the photo and the drawing in Superimpose app. I toggled between the paintbrush and eraser masking tools using the soft brush setting. If I took away too much I switched to the other to paint it back in. The app is very forgiving, but it doesn't give me textured results only blended or hard edges. I did the best I could when I whipped up the examples below.