HTML 5 is of course intended to be used by all kinds of Web devices, but there are certain extensions to Javascript that are primarily aimed at mobile devices, not the least location.
I found these useful pages through a simple googling:
- Mobile HTML5 – Tutorial- Your First Mobile HTML5 App – The Basics, Forms, and Geolocation…
- Mobile HTML5 – compatibility tables for iPhone, Android, BlackBerry, Symbian, iPad and other …
- HTML5 in mobile devices – Wikipedia, the free encyclopedia
- HTML5 from a Mobile Perspective « Cloud Four
From the last one I picked these benefits compared to previous HTML versions:
- Offline Support
- Canvas and Video
- GeoLocation API
- Advanced Forms
This means it’s mostly Javascript from now on, whether you like it or not.
You can stay native as well, but it makes a lot of sense to know HTML 5 to achieve cross-platform support with only one implementation. Especially if you develop apps that complement on-line services and where you don’t charge for individual app downloads, but rather use subscription- or ad-based revenue.