Google Latitude for iPhone and iPod touch is a location-based web app running in Safari.With the Google Latitude web app users can see the location of friends on a map and modify r
privacy settings.
around the world. Press the "blue dot" to be taken to the approximate current location on the map with My Location. It works thanks
to Safari now supporting the W3C Geolocation API.
To try Google Latitude, type google.com/latitude into an iPhone's browser. 
Google worked closely with Apple to bring Latitude to the iPhone in a way
Apple thought would be best for iPhone users. After Google developed a
Latitude application for the iPhone, Apple requested that they release
Latitude as a web application in order to avoid confusion with Maps on
the iPhone, which uses Google to serve maps tiles.
in the background on iPhone (which applies to browser-based web apps as
well), there is no continuous background location updates
in the same way that it works for Latitude users on Android, Blackberry,
Symbian and Windows Mobile. Location is
updated every time the app is launched and then continuously updated
while the app is running in the foreground.
The Google Latitude web app currently supports iPhone/iPod Touch OS 3.0
or above. For now, it's available in the US, UK, Canada, Australia, and
New Zealand, and we hope to bring it to more countries soon.