How to launch Google Maps on iPhone via web link?

You can use apple's interface which is a bit more intelligent when using different browsers and devices:

http://maps.apple.com/?q=51.507269,-0.127695

Clicking the above url on the following devices:

iPhone|iPad:Opens Apple maps app

Android:Gives you a choice to open in either Google Maps App or Google maps website

Windows Phone:Opens Google maps mobile website

Windows 8 Desktop: Opens Google maps website

Apple OS Desktop: Opens the new maps app (Mavericks)!!

For more info see:Apple URL Scheme Reference

To open Google native app you need to write:

[[UIApplication sharedApplication] canOpenURL:[NSURL URLWithString:@"comgooglemaps://"]];

Example :

comgooglemaps://?q=Pizza&center=37.759748,-122.427135

I just tested this and it worked in pulling up Google Maps instead of the default Apple Maps application.

<a href="comgooglemaps://?center=40.765819,-73.975866&zoom=14&views=traffic">Testing Maps</a>

However, after deleting the Google Maps app for iOS, the link fails to open anything because that schema is no longer available and doesn't fallback to a generic maps link... almost seems like you would need to provide two links for Google Maps for iPhone and another generic Apple Map link...