You've been able to paste a KML file straight in to Google Maps for a while, as of today, Google Maps for Mobiles supports this too. Sweet.

http://services.google.com/marketing/links/trekfan2006/

Should work really well if you want an easily accessible list of locations straight on your mobile. I'm think intineries for holidays would be a perfect example, or possibly an online treasure map application that people play on their mobiles...

And there are many videos about that :)
http://video.google.com/videoplay?docid=2705703124679991020
click on the link "from user" ;-)

http://www.google.com/trekfan
[via Google Maps Mania http://googlemapsmania.blogspot.com/2006/08/google-maps-for-mobile-now-supports.html]

note : KML there is used just for addresses. You can't see 3D Buildings or layers