They make analog/SPI thermopile image sensors. The 8x8 gives 70fps, the 32x31 does 18fps.
Cost in reasonable (to stock) quantities starts around $100 and goes up to around $400 depending on resolution and optics. Their demo modules and application modules can run up to $2k, so way outside most people's wants. These demo units run PIC24's, so these do NOT need super fancy controllers. And at max framerate the data stream is reasonable for a mid to high end microcontroller to handle and process onboard.
Strange ideas, rambling technical thoughts
(yes, I'm working on a real website eventually)