New Relic is a popular tool for web developers to monitor server load and crashes.
Recently, they have introduced New Relic for Mobile!
Similar to what it does for web developers, it now helps mobile developers track API calls (how long it took) and deliver crash reports.
This is however, not new. Crittercism and Crashlytics have been available for a long time.
I personally recommend Crashlytics, since they have been acquired by Twitter recently, and hence even their Enterprise version is free.