Samsung Galaxy S4 is loaded with lot of sensors. Ambient temperature and humidity level are 2 of them. Well, you can get these values with Comfort level feature in S Health application. Or in Temp-Humid test in FactoryKeystring application (How to test Galaxy S4 hardware functions?). But that require few clicks here and there. So XDA Developer, bala_gamer developed a nice Ambient Weather for Galaxy S4. You can get ambient temperature and humidity level straight from it.