I've been working on this off and on for several years now. The main stumbling block has been a thermal camera at an affordable range. Previous experimentation has shown the RaspberryPi, with sunglasses-style personal display (sold for watching video on trains and such) appear to likely fill the CPU and HUD side of the equation. Recent innovations in thermal cameras (FLIR One) appear to have finally brought costs to the point where this can be done within the desired price point.

The last piece of the puzzle is likely a FLIR Lepton module, which is currently in transit to me in New Zealand. Once this arrives I'll be testing and building a prototype, will post progress.