Sense and Avoid Systems (SAASs) are one of the last technical challenges for the safe integration of Unmanned Aerial Systems (UASs) into the U.S. National Airspace System (NAS). While military applications still dominate UAS use, civilian UAS usage is expected to grow dramatically over the next several years. However with this growth, there are significant air safety concerns. SAASs have been proposed as potential solutions for air traffic collisions and obstacle avoidance, but the technical implementations have been largely unsatisfactory. The development of the Next Generation Air Transportation System (NextGen) surveillance tracking technology known as Automatic Dependent Surveillance-Broadcast (ADS-B) has been proposed as one of the potential solutions. This technology, mandated to be in all aircraft by 2020, is designed to improve situational awareness for pilots and improve air traffic management but may also be utilized by UASs. However there remains implementation issues and regulatory issues, especially for small UASs (SUASs) that are expected to be used significantly by civilian operators. This paper examines the use of ADS-B in future SAASs and their implementations in SUAS for domestic use.