BatteryBot

Shows your battery charge level (percent) as an icon in your status bar, with temperature, health, voltage, and time since plugged / unplugged in the notification area. It also has user-configurable alarms, logs, and widgets.

Automatic time-remaining estimates based on recent usage Several icon sets (including fully configurable green, amber, red, and black icons) Small (1x1) and large (4x1) app widgets Notification (with status bar icon) is now optional -- can be used as just a desktop widget Battery logging. You can log the battery state (charge, status, voltage, temperature) and browse the logs on the phone or export to CSV. Manually or automatically disable / re-enable device lock screen / lockscreen / keyguard Alarms (full, charge above X, charge below X, temperature above X, or health failure) Control the notification priority on Android 4.1+ (For example, you can set to "minimum" to hide the icon but keep the notification in the tray.)