The development of ultra-low-power (ULP) electronic devices has opened up opportunities for disruptive systems like the Internet of Things (IoT). The main concern is the security and privacy issues of the huge amount of personal, sensitive, or safety-related data being processed in these systems. Ensuring security in these ULP systems poses additional challenges than in computers, because of power and cost constraints and physical accessibility by attackers. To solve these problems, innovations in both software and hardware are needed. This article presents a survey of state-of-the-art hardware designs optimizing the tradeoffs between security, power, and costs (including design and manufacturing). The authors analyze the connections between hardware specs and system demands to bridge the gap between research conducted in different communities. They also identify open problems in designing future ULP secure hardware.