Battery is the main aspect of any smartphone. To keep healthy your battery:
Prevent your cell phone from over charged.
Timely charged your cell phone when battery low.
By using battery indicator application, your phone will be ringing automatically
1) when battery fully charged
2) or low
3) or reached to user defined value (you can set alarm when battery reached to specific % of battery).
you can also send #message to your favorite number when battery will be low and notify him that you have not enough battery and your cell might be off.
Here is application link: