We've been using Crittercism in the past and recently switched to Crashlytics, unfortunately memory crashes are one of the few exceptions (hah) to the rule, as they are SIGKILLs from the OS.
Another commenter recommended touching a file at launch and at sleep to track untraceable crashes, which we do for various other reasons, but don't upload the stats. We may begin doing this.
Another commenter recommended touching a file at launch and at sleep to track untraceable crashes, which we do for various other reasons, but don't upload the stats. We may begin doing this.