Google announced you can now get iOS install sources via Google Analytics when you have AdMob installed on your app.
Now you can tell what lead people to download your app. Was it a banner ad? Organic search? Paid search ads? Social media, etc.
So if you are doing any marketing to promote your app, you can make sure your marketing dollars are being spent properly on your apps.
Here is a screen shot showing you what you might see (click to enlarge):
To set this up, read these technical guidelines.
Forum discussion at Google+.
