Your phone likely has a water sensor in in it to help manufacturers and resellers prove if it’s been exposed to too much moisture to qualify for warranty service or replacement. Except in rare circumstances, a phone that’s a dunking or spill victim is ineligible for complimentary warranty repair. Knowing where this sensor is can help a user determine if they are likely to get warranty service or replacement if their phone is damaged or non-functioning. It might also help you know what to specifically protect if you are in a rainstorm.
Tested.com has a list of popular cell phones and shows where each of the handsets’ water sensors are located. For example on Apple iPhone’s and iPod Touches you will find the sensor either in the headphone jack (see image) or in the dock connector. There is a small white spot that will turn red if exposed to moisture. This can be problematic as the phone itself may not be submerged but water could get into just that location causing the sensor to turn from white to red and indicating exposure to water. There is even a lawsuit over this as some Apple customers claim their phones were not submerged in water but the sensor’s color changed. I personally experienced this with an iPod Touch that stopped working. The hard drive failed. But since the water sensor was a light shade of pink, Apple would not replace it though it was still under warranty.
Other manufacturer handsets covered in the story are the HTC EVO, T-Mobile G1, Blackbery’s various models, the Palm Pre, Motorola Droid, and the Samsung Galaxy.