Very recently, one of my friend who happen to have started using iphone just now was very much pissed off with the iPhone battery, he asked whether there is any setting or iphone app which could give him iphone sound alert at low battery level. iPhone did not last him for the whole day even with moderate use, I gave him some tips on how to turn off features on iphone like bluetooth, wifi and other to save battery.
After thinking about an app which could give you sound alert can be really useful for many people as this would help them find a charge point before their iphone go dead. Although iphone does give you a silent prompt when iphone battery reaches critical low level which is 20% by default on iphone.
Now after installing some apps on iphone, you can hear sound alerts as well when iphone reaches low battery level. One such app is called Battery Alert for $ 0.99 which is designed to ensure you always know when your battery needs a little extra juice. When its warning threshold is met, it will play your chosen sound in the background, even if your device is doing something else or locked and in your pocket. It also lets you change the low battery level at which it will sound an alarm, as shown in the image below.
Now if we talking about a jailbroken iphone there are more ways to make your iphone produce a sound alert when it reaches the critical battery level. The most app on cydia is PowerAlerter which is a paid app under modmyi repo, it alerts you with sound or song selected for your choice from iphone music as shown in the image below.
However the bad news is that, PowerAlerter does not work on iOS as if now. But there is another tweak called PowerAlert Vibration on cydia which comes for free, but it works differently as it does not produce a sound rather it make your iphone vibrate at low battery
Recently there is a new tweak called LowPowerBanner released on cydia for ios 5 or later, but on the other hand it does not cause any sound alert but pops up a banner when iphone have low battery which is around 20% by default for any iphone. The alert looks like as shown in the image below.