The availability of a reliable and precise tracking system for relief units operating in mission critical scenarios would drastically improve the situational awareness and thus facilitate the mission planning and accomplishment as well as increase the safety of human resources. Thus, the demand for such a system is very high both in the military and in the emergency and crisis intervention domain. While there are solutions like GPS for the localization in open areas, problems arise in urban scenarios and indoors due to insufficient or failed signal reception. For indoor use, multiple alternative localization concepts exist that are suited for different use cases and expose varying properties in precision, complexity and required preconditions. The deployment within mission critical scenarios implicates explicit restrictions and requirements so that only some of the techniques are adept or have the potential of being used here. This article identifies the commonly issued requirements to an indoor tracking in mission critical scenarios and introduces basic techniques for position estimation. Subsequently, existing indoor tracking systems specifically in the field of mission critical scenarios are reviewed with a focus on their capabilities in terms of reliability and accuracy. By doing so, an overview of current approaches in this field is given. Furthermore, the most adept techniques are classified with respect to the requirements within mission critical scenarios.