iOS (Jailbroken): Now that Google Maps is out for iOS, we don't have to resort to using Apple Maps. However, there's no way to get iOS to open map links in Google Maps instead of Apple Maps. Fortunately, this jailbreak tweak will do just that.
MapsOpener essentially changes the default maps app to Google Maps. This means when you open a link to a map online or from an app, it opens in Google Maps instead of Apple Maps. It's simple but incredibly handy if you've decided that Google Maps is the better default map app. If you're not jailbroken, you can at least work Google Maps into Siri. You can find MapsOpener in the Big Boss Repository in Cydia.