In this paper we present an overview on the development and standardization of ultra-wideband systems, technical aspects of the IEEE 802.15.4 standard, and improvements made by the 802.15.4z amendment. We also explain the basic workings of a physical access system, the desired seamless access experience and how ultra-wideband technology can enable it. In addition, we briefly compare ultra-wideband to facial recognition access systems. We conclude by mentioning how ultra-wideband technology may extend to other related applications.