I'm looking for a presentation or slideshow app on iPad that can output a true 16:9 image to an external monitor using the digital a/v adapter / HDMI. This requires explicit support in the app (which I've written into my own app), rather than using the native screen mirroring of the iPad 2. Ideally it would remove borders completely using UIScreenOverscanCompensation, but a few black pixels around the edge would be acceptable.
So far I've tried QuickOffice, but that doesn't expand the slide to fill the entire screen, and displays pillarboxed. I've also used the built-in Photos app, which has the same problem. Apple are ambiguous about whether Keynote will use the full screen on an external monitor.