In speaker view, a thumbnail view where you could navigate and advance to slides out of order by clicking a thumbnail.
If you could add another view with small thumbnail previews of all the slides so that a live presenter could go back to a slide by clicking its' thumbnail image. This would be helpful during Q&A or if a student or attendee was advancing slides on behalf of the speaker in order to keep the web audience in sync.
I'd like to see this take even further-- I'd like those slide thumbnails in desktop mode for both the viewer and the presenter. It's super annoying to have back track thru a massive slideshow to get to a slide further up the deck. It would be great to see a thumbnail carousel, hide/un-hide toggle-able, where the user can click on any slide to jump to it.