A Water Sensor in iPhone and iPod Touch!?

Let's say you drop accidentally your iPhone in water (not sea water as salt will be easily spotted), you can always try to send it back to Apple Support for having it repair under warranty. To avoid such behavior, Apple has included a water sensor in the iPhone and in the iPod Touch:

At the bottom of the jack plug you can see a white disc that will irreversibly change color when entering in contact with water. So one would not need to open an iPhone or an iPod Touch to ensure it stopped working due to an unexpected bath.
Hereafter it the same disc in the iPod Touch.

We did not have the opportunity to check if such system was also added to the last iPod nano and iPod Classic.