Veteran web usability consultant Jakob Nielsen recently gave an "At Google" talk about mobile usability and where it's headed. Google has now made the talk available for all to see.
If your'e developing a mobile app or site, you may want to give this guy an hour of your time. He's one of the biggest names in usability, and has plenty of advice.
Nielsen, an early consultant at Google years ago, discusses usability guidelines, how they relate to technology, designing for platform, engineering and how to bring usability to the masses.
Nielsen was a Distinguished Engineer at Sun Microsystems in the mid-nineties. He co-founded usability consulting company Nielsen Norman Group, and writes a web design newsletter called Alertbox. He is also credited with founding the "discount usability engineering" movement, which helps designers make changes to their interfaces quickly and inexpensively.