Apple released an update to the iPhone, pushing it to OS 3.1.3 which contains bug fixes and improvements. It improves the accuracy of reported battery level, though unless it lengthens the battery life, I’d not really want to see how battery life my iPhone has at the end of the day…
Other fixes includes resolving issue where third-party apps would not launch in some instances, fixing bugs which might cause an app to crash when using the Japanese Kana keyboard.
This update is available for all iPhone and iPod touch and you can download it via iTunes.
Just like how you would when updating your OS X on your Macs, always remember to backup in case accidents happen.