Yes, with regards to basic functionality, it is a substitute. It's also known as a mobile-version (similar to Facebook, Twitter, etc). You have to remember to target various screen sizes though.
-320 x 480 of course, iPhone, iPad, Android, etc. You would need to target these with @media queries:
Code:
@media screen and (min-width: 321px) and (max-width: 480px) {
}
... you need more
No, I don't believe you can. You cannot access a user's location unless there was a security warning. I don't think older phones support
geolocation, I remember it was in modernizr. In Safari, you get a security pop up when a website is trying to access your location.
From the geolocation link:
Browser Support Chart:
http://caniuse.com/geolocation (take a look at the mobile support)