Weather features:
Temperature, even without a sensor in the watch if the website can map your location then it should be able to see the temperature in the zip code via google or a weather service, (temp, wind, humidity, temp change over time, etc.). This is useful because when running or cycling you can track performance changes on a 110 degree day vs 75 degree day. I personally wouldn't want the sensor to be in the watch because my body temp could affect the reading. *And don't give me that do a manual update response, i bought the watch because i'm lazy and don't want to keep track of things manually!
Health Tanita features:
They have this for the cheap watches how about let the premium buyers tap into this feature as well.
http://www.tanita.com/en/bc1000/
*Core Temp Indicator:
Added after XFATMAN's comment. Might not be too realistic...swallow the pill, it communicates with the watch recording core temp...will have to think on if the pill should be reuseable
Lance's core temp reading