iOS: If your iPhone battery can't quite make it through the day, your apps may be draining your phone. Normal finds those apps sucking down your battery and makes suggestions on how to resolve it.
The app collects data about your usage (see the privacy policy) and compares it with other Normal users to find those apps that typically drain the most battery. If it finds a hog, it then gives you tips on how to change the way you use the app to reduce battery usage.
My battery hog was Facebook Messenger and Facebook—no surprise there (try the mobile site instead). Data enthusiasts will like the crowd sourced data comparing your iPhone's battery life to other models of your phone.
Normal: Battery Analytics ($0.99) | iTunes App Store via TechCrunch