@elyw I'd leave bookmarking to 3rd party, e.g. Mendeley. #bhlib specific issues incl. displaying DjVu files, and highlighting taxon names
rdmpage
Quick mock-up of a possible BHL iPad app (made using OmniGraffle), showing a paper from BioStor(http://biostor.org/reference/50335). Idea is to display a scanned page at a time, with taxonomic names on page being clickable (for example, user might get a list of other BHL content for this name). To enable quick navigation all the pages in the document being viewed are displayed in a scrollable gallery below main page.
Key to making this happen is being able to display DjVu files in a sensible way, maybe building on DjVu XML to HTML. Because BHL content is scanned, it makes sense to treat content as pages. We could extract OCR text and display that as a continuous block of text, but the OCR is sometimes pretty poor, and we'd also have to parse the text and interpret its structure (e.g., this is the title, these are section headings, etc.), and that's going to be hard work.