Getting to wounded soldiers on the battlefield is a precarious task, and medics have a very high casualty rate. It is therefore a vital importance to prioritize which soldiers to attend to first. The first step is to detect life signs - if a soldier is dead or alive, and prioritize recovery of live soldiers. The second step is to obtain vital signs from live soldiers, and use this to prioritize which are in most urgent need of attention. Our team at Kai Sensors, University of Hawaii and University of Florida is developing Doppler radar heart sensing technology that provides the means to detect life signs, respiration and/or heart beat, at a distance, even for subjects lying motionless, e.g., unconscious subjects, wearing body armor, and hidden from direct view. Since this technology can deliver heart rate information with high accuracy, it may also enable the assessment of a subject's physiological and psychological state based on heart rate variability (HRV) analysis. Thus, the degree of a subject's injury may also be determined. The software and hardware developments and challenges for life signs detection and monitoring for battlefield triage will be discussed, including heart signal detection from all four sides of the human body, detection in the presence of body armor, and the feasibility of HRV parameter extraction.