Reading a book on the iPad, with the whole as a mosaic on the wall. A little dot above the mosaic indicates your position.
Relative movement (next page, previous page) by swiping the iPad. Absolute movement (jump around within the whole) by lasering the wall. You can also skim around the whole without "losing your place" by holding a thumb down on the iPad while lasering.
(Reminder, as always, these explorations aren't intended to be immediately usable or "the right thing". They are shining a flashlight into a dark room that's making interesting noises.)