What's causing the battery drain on my device?

Apps cannot access the process information and battery statistics directly so this feature cannot be implemented by System Status itself.

However, since iOS 8, there's a built-in functionality in iOS to give you some basic battery usage info. You will find it under Settings->Battery in iOS 9 or Settings->General->Usage->Battery Usage in iOS 8. You'll find battery usage sorted by apps for the last 24 hours and 7 days.