For temperature-linear values you need a InGaAs SWIR or Bolometer sensors. CMOS/CCD range is approx. 400-1100nm. Thermocameras have 750-1400nm (bolometer sensor) or 750-1700nm (InGaAs). The cheapest are the bolometers as they are uncooled due to better control of dark current, whereas InGaAs need peltier cooling, making them very expensive. These can be used with bandpass filters for hyper spectral imaging, though, while bolometers are only thermal imagers. The cheapest I know of is Micro Epsilon Thermal Imager 120Hz 160x120. It is USB2.0 and comes with a nice software to make temperature curves and triggers and record the images. It can have radiosity or thermo linear values in 16bit.
What you can do with the CMOS/CCDs is make NIR images and NDVI vegetation indexes (if you use a longpass filter over green and do some math on the rgb values), because chlorophyll reflects NIR light and the sun has a lot of it. You can also do night vision if you bring your own cheap chinese NIR light source from dealextreme. If you polarise the light and cross a polarising filter you can make blood veins contrasty.
I found this table showing the wavebands emitted by steel at high temperatures:
At 480C it starts to show in the highest visible part of red, and then it moves down through orange, adding green and blue, so it is white. In NIR it should start to show a bit before, maybe around 400C. So if you kill all other NIR light sources, you can measure the temperature of hot steel. But you can also do that with RGB.