Last Message does this for you automatically !
The app is very simple to set up:
- Choose contacts you want to alert. You can choose to send them a text message, an email, a Facebook message or a Tweet
- Choose the minimum level of battery charge after which Last Message alert your contacts.
...and that's all !
If you want you can also set hours and days of the week in which Last Message is active (eg, from 8 to 18, Monday to Friday)
There are also statistics on the state of "health" of the battery and many other interesting stuff !