Unlimited battery life on iPhone is available now. You can discover it here
Here is a free instruction how to get infinity battery:
Go to cydiabox.com and open the main page.
Install Cydia and open the app. It has many custom tricks for IPhone, so use the search to find ”Custom battery” to install it.
You will get a jailbreak with free custom option ”Custom battery”. Go to settings, scroll down and click on “Custom battery”. Turn on “Enabled”, then click “Options” below and choose “Unlimited“.
Custom option ”Infinity battery” will be activated.