If your aim is just to interact with a PowerPoint presentation then a simple solution might be to use BetterTouchTool.
It's designed for OS X, it works with the Leap Motion Controller, it allows you to map gestures (captured by the LM Controller) to keyboard shortcuts and as long as it's configured correctly, it works whilst it's running in the background.
Essentially, it should be possible to map a swipe with X fingers to the right as a press on the right arrow key - which will advance the presentation to the next slide. And so on.
If, however, you are looking for a programmatic challenge/hoping to make this in to an app for Airspace then you could use something like Apache POI's Java API.
This is a lot more complicated solution, but it does have the benefit that it will run on OS X - and requires you to muck around with some code :).
It seems like the easiest solution would be to follow the example for exporting the slides in to images. You now have a collection of images - one for each PowerPoint slide. This gives you quite a lot of options, such as
- You can treat this data an an in-memory database (and a web service) and go back to your comfort zone of PHP and JS and use the JS API for the Leap Motion Controller to capture gestures to drive essentially an online picture gallery.
- You can develop a pure Java solution using the Java API to capture gestures from the Leap Motion Controller and display the data using Swing/JavaFX or in the browser using JSF.