Keynote presentation in conjunction with other app?

"You can use the H keyboard shortcut while the presentation is running. This (according to the help displayed using the ? shortcut) is used to ""Hide the presentation and switch to last application used"".

If you make sure the application you are wanting to demo is the last application used, you can do the following

Go through your presentation until you get to the Demo slide
Press H to switch to your application
Demo the application
Use ⌘ + Tab to switch back to Keynote
Your presentation resumes from the Demo slide."

"It's not likely. The Mac OS is based on one application being the active application. When you switch to another app, regardless of what you've told Keynote to do the new app is now active and will do whatever if normally does. The reason that Apple's Demo slides work is exactly because they use a different input source. The keynote never stops running.

Perhaps there is some way of making this happen that I'm not aware of but it will almost surely not be worth the time and effort. In the end most people should be focusing on your demo and not the transition."