As of the date of this post, you can control a presentation through Bluetooth for Keynote, PowerPoint, and PDFs on your iPad using your iPhone with 2Screens (and their iPhone remote). It's not as nice as Keynote, but it is handy for PDF documents.
The Apple Keynote remote app, which works nice on the iPhone, is wifi only. Yes, I could bring my MacBook Pro and set up an ad hoc network, and connect my iPad and iPhone to it, and remote control the iPad from the iPhone -- but then I might as well just use the MBP for the presentation.
The iPhone and iPad CAN communicate through Bluetooth, as the excellent PhotoSync app shows. [This app allows you to shoot pictures on your iPhone, and then transfer them by bluetooth to the iPad for editing.] The Apple Keynote Remote app simply does not do this, at this time.
With an iPad 2, there is full mirroring of the iPad on external displays. The VGA connector does not support power while connected, but the other connectors do. Perhaps a future VGA connector will support power as the latest HDMI connector does.
I can not find any Bluetooth hardware for advancing slides on an iPad, so far. I remain hopeful...