Maybe as a human presence detector for security, control of musical instruments, monitoring vital signs. In all those cases you probably don't want a radio emi

Maybe as a human presence detector for security, control of musical instruments, monitoring vital signs. In all those cases you probably don't want a radio emitter near other equipment (especially in a hospital). For security systems, say as a human presence detector, you may not want to advertise your security system has a radar sensor by broadcasting RF. I think there are some research papers on using passive radar for vital signs monitoring. Indoor localization would be a good use also.