Digital infrared thermal imaging (DITI) cameras use infrared imaging to give thermographs that are used to diagnose different ailments, detect cancers and monitor the healing process. The medical infrared thermographic cameras were adapted from industrial equipment to be more affordable.

Not much. Some put the span of the IR spectra at a lightly different place than the thermal span, but the difference is marginal.

Sir William Herschel noted infrared back in the 1800s. But, there were three companies, Texas Instruments, Honeywell, and Hughes Aircraft, credited with modern technology in infrared detectors and imaging.

FLIR is the global leader in thermal imaging infrared cameras.

No. Bluetooth and infrared devices operate on separate frequencies.