Ask HN: what app would you use for this job?

I am currently working as a consultant for a company in the tourism/travel/leisure sector. Sometimes I have to sit to the side of one of their users and ask them to work through the steps they have to follow while using a legacy system (partially exposed via web, partially via character interface). I noticed that what I tend to do is to take notes on a notepad, and supplement these with screenshots I ask the user to take, or just shoot with my iPhone. Considering I also have an Android tablet which so far I haven't found much use for, I was wondering if there is an app (either iOS or Android) that could allow me to take notes (typed via keyboard), interspersed with pictures taken with the device camera, and annotated with freehand writings, doodles, drawings, all as a single document (a sort of vertically infinite scrolling sheet) and finally export it to some sane document format to postprocess on a desktop. Thanks for any suggestions.