WeatherSignal launched on the Play Store today, and you may want to check it out. It uses your device to give you information about the weather, and crowd sources that information to record weather patterns on a local level. Using sensors and some clever algorithms, it can tell you pressure, temperature, light intensity, humidity, and magnetic flux. However, not all of those features will be supported by all phones.
Light intensity and magnetic flux are easy, as they are simple sensor readings and are available on most devices. Pressure requires a barometer, but many devices (including the entire Galaxy S line from the third and up and the Note II line) already have them. Humidity can only be told by a Samsung Galaxy S 4, as it has a hygrometer. Accurate temperature is also Galaxy S 4 exclusive, but any phone can tell temperature with some clever coding on the developers part.
Their temperature algorithm uses battery temperature and converts it into ambient temperature. It’s an approximate number, but it’s awesome that they figured that out. It didn’t seem to want to work for me indoors in a warm room (pretty sure it isn’t 40 F in here), but you may find it works well for you. And of course, updates will work out the kinks from launch day. Hit the source link to try it out!