I don't think it's possible to embed google maps in your app (and you may never be able to either due to licensing issues) - instead you should link to the map using the approprite URI - the standard way of communicating with other apps - the iPhone will open this in the native Google Maps application. People can then return to your app when you are done.
Take a look at the Vicinity app for an example of this. You'll have to save your application state so people can return to where they left off when they return to your app.