Measure temperature on a moving engine valve: transfer voltage and reading wireless?
A good way might be to use a pyrometer. It is an optical device that receives the heat/light emitted by the object whose temperature needs to be measured and then uses part of that "spectra" to calculate the temperature. 

It relies on understanding the "black body" radiation from the object and its emissivity: -



I've used it for temperatures as low as 600 degC on aero-engine turbine blades but, in theory, can be used much lower. You can pipe the radiation off in a suitable optical fibre and it's a non-contacting method.

It does rely on filtering a small fraction of the bandwidth of the emitted radiation and there are optical filters that can do this for you. I've used an optical filter and the photo-diode's natural spectral response to select the 1.7 \$\mu\$m part of the emission. If you can find a device and filter that is good for band-pass filtering about 3 \$\mu\$m then you should be in business.

The only area I'm unsure of is the sub 600 degC region but if you are looking to measure temperatures at or above this point it can certainly be done.