Meet the BLUEmometer: a cool thermometer that connects to your iOS/Android device via Bluetooth to measure the temperature of almost anything you can think of. It can show you the temperature of your pool water, wine, baby milk, and everything else. The device is hermetically sealed and does not get damaged by liquids. The BLUEmometer is pretty smart. It provides you with instant temperature readings and can even notify you when the right temperature has been reached.
Since the device is waterproof, the battery is not replaceable. But it does last for 10000 temperature measures, which is about 3 years. The developers are working on a version with a replaceable battery but they will need your support on Kickstarter.