How can I use my Apple bluetooth keyboard for keyboard navigation on my iPad?
I am sorry to say that I am unaware of any apps (jailbroken or otherwise) that add keyboard navigation to the iPad.

According to GigaOm, the following shortcuts do work:


⌘C Copy selected text
⌘X Cut selected text
⌘V Paste
⌘Z Undo
⌘shiftZ Redo
⌘↑ Go to top of document
⌘↓ Go to bottom of document
⌘← Go to start of line
⌘→ Go to end of line
⌘⌫ Delete to end of line
⌥⌫ Delete previous word
F1 Make screen dimmer
F2 Make screen brighter
F7 Skip back one song
F8 Play or Pause Music
F9 Skip forward one song
F10 Mute Volume
F11 Decrease Volume
F12 Increase Volume 
⏏ Show or hide onscreen keyboard