Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
This was added before any standardization to meet aggressive EU deadlines, so there’s not really much besides Apple’s current documentation on it. I do not believe extensibility is defined (eg there may be limits supplying points of interest and the like).
Thanks!

Really weird, not even Siri requests are intercepted with the custom geo-navigation:// url scheme Apple state you need to support. I'd thought that all Apple internal requests to Apple Maps were routed via this scheme
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.