Every once in a while, you get that annoying person that keeps messaging you that wonders why you aren't answering them. There are also those times when people ask you if they can borrow your iPhone, and when you really don't want to be rude, but also really don't want them to use it, you need a good excuse.
Available now for free in Cydia is a new jailbreak tweak called SorryLowBattery
by iOS developer rob311 that will allow you to fake your battery percentage to be whatever you would like it to be, as shown above.
This tweak is perfect for gaining the excuse you need. It will let you change the battery percentage easily, on the fly. It comes complete by not only changing the numeric value, but also by showing the red low battery icon whenever you set a percentage lower than 20%.
It adds a preferences pane to the Settings application where you can configure your custom battery percentage, and enable or disable the tweak on demand:
When you change the setting, a respring is not necessary. Just close the Settings application, and your changes will take effect before your eyes.
Now, when someone is bothering you, or you don't want to give them your iPhone to use, just tell them, "sorry, my battery is low" and now, you can even show them.
If you would like to give SorryLowBattery a try, it's available for free right now in Cydia's BigBoss repository. The tweak requires iOS 7 to be installed.
iPhone 5 running iOS 7.0.6