Smartphones provide many ways to engage the world. There are apps to help you drive better, run faster, become greener, find more birds and meet new people.

But smartphones don't just make the world better, they can make themselves better, too. These efficiency apps can help you get more battery life, limit data usage and maximize your mobile device's performance.

Carat (Free; iOS, Android) - If your smartphone is on an energy binge, you can put it on a diet using Carat. This program was designed as an experiment at UC Berkeley, and it really works well.

Carat tracks information about your battery usage and program usage. It sends the anonymous information to a secure server and about a week later begins making customized recommendations to maximize your battery life.

It can even help you visualize your usage through graphs and compare your battery efficiency to other users.

Onavo Count (Free; Android) - I've told you about Onavo Extend, the almost magical app for saving on data use. This app takes the savings a step further.