Wearable activity trackers (WATs) have become increasingly popular in recent years. However, few studies have examined the critical aspects of their utility, privacy, and security. This survey reviews 236 studies to understand the benefits, privacy implications, and security vulnerabilities of WATs. The survey reveals that these devices expose users to several threats, such as the potential to infer private information like personality traits. While many studies focus on users' privacy perceptions and behaviors, few explore technologies to better protect users' privacy. The survey contributes to systematizing knowledge on the utility, privacy, and security of WATs, shedding light on state-of-the-art approaches and discussing open research opportunities. WATs are smart devices that record human activity data, often in the form of wrist-worn bracelets and watches. They have become extremely popular, with a projected market value of 114.4 billion by 2028. Researchers have studied WATs from various perspectives, including design, psychology, health, and security. Three critical aspects of WATs are utility, privacy, and security. These devices can empower users to improve their well-being but also expose them to privacy risks due to the sensitive nature of the data they collect. Users' perceptions of WAT utility and privacy are interwoven, and they often perform risk-benefit analyses before using technology. Security is also crucial, as it plays a pivotal role in mitigating risks where data must be protected from unauthorized access. The survey found that WATs can provide various benefits, including physical activity, health improvements, medical benefits, and social benefits. However, the increase in physical activity might not always be sustained after users stop using WATs. Users also have different motivations for using WATs, such as logging activities, setting goals, and self-reflection. Social usage and data sharing are common, with users sharing data with friends, family, and strangers to compete or support each other. However, users' willingness to share data depends on the type of data and the audience. The survey also identified several usability issues with WATs, including difficulties with synchronization, navigation, and text entry. Additionally, the accuracy of WAT data can be a concern, as it may not always represent actual physical activity. Users have differing requirements for accuracy, with some caring about the accuracy of WAT data and others not. The survey also found that WATs can be risky for users' privacy, as they can be used to infer personal information, such as health metrics, activities, and location. Adversaries can use this information to target users or discriminate against them. The survey discusses privacy policies, regulations, and ethics related to WATs. Privacy policies are used to inform users about data collection and usage practices, but their usability and compliance with users' privacy needs are still under debate. Many studies have reviewed WAT-related privacy policies and identified issues such as a lackWearable activity trackers (WATs) have become increasingly popular in recent years. However, few studies have examined the critical aspects of their utility, privacy, and security. This survey reviews 236 studies to understand the benefits, privacy implications, and security vulnerabilities of WATs. The survey reveals that these devices expose users to several threats, such as the potential to infer private information like personality traits. While many studies focus on users' privacy perceptions and behaviors, few explore technologies to better protect users' privacy. The survey contributes to systematizing knowledge on the utility, privacy, and security of WATs, shedding light on state-of-the-art approaches and discussing open research opportunities. WATs are smart devices that record human activity data, often in the form of wrist-worn bracelets and watches. They have become extremely popular, with a projected market value of 114.4 billion by 2028. Researchers have studied WATs from various perspectives, including design, psychology, health, and security. Three critical aspects of WATs are utility, privacy, and security. These devices can empower users to improve their well-being but also expose them to privacy risks due to the sensitive nature of the data they collect. Users' perceptions of WAT utility and privacy are interwoven, and they often perform risk-benefit analyses before using technology. Security is also crucial, as it plays a pivotal role in mitigating risks where data must be protected from unauthorized access. The survey found that WATs can provide various benefits, including physical activity, health improvements, medical benefits, and social benefits. However, the increase in physical activity might not always be sustained after users stop using WATs. Users also have different motivations for using WATs, such as logging activities, setting goals, and self-reflection. Social usage and data sharing are common, with users sharing data with friends, family, and strangers to compete or support each other. However, users' willingness to share data depends on the type of data and the audience. The survey also identified several usability issues with WATs, including difficulties with synchronization, navigation, and text entry. Additionally, the accuracy of WAT data can be a concern, as it may not always represent actual physical activity. Users have differing requirements for accuracy, with some caring about the accuracy of WAT data and others not. The survey also found that WATs can be risky for users' privacy, as they can be used to infer personal information, such as health metrics, activities, and location. Adversaries can use this information to target users or discriminate against them. The survey discusses privacy policies, regulations, and ethics related to WATs. Privacy policies are used to inform users about data collection and usage practices, but their usability and compliance with users' privacy needs are still under debate. Many studies have reviewed WAT-related privacy policies and identified issues such as a lack