Link to iPhone map App from HTML page

A link to http://maps.google.com/maps will automatically open in the map application

You can set a destination address (daddr) and start address (saddr) in the link:

http://maps.google.com/maps?daddr=San+Francisco,+CA&saddr=cupertino

You can see some more options at:

https://developer.apple.com/library/archive/featuredarticles/iPhoneURLScheme_Reference/MapLinks/MapLinks.html

Here is a javascript function that creates the link:

function mapLink(myAddress) {
    return 'http://maps.google.com/maps?q='+escape(myAddress);
}

This works great on the iPhone.

If you use the standard link that would display a map in the browser, it will automatically open in Google Maps on the device. That includes links that show directions.