An activity tracker, also known as a fitness tracker, is a device or application for monitoring and tracking fitness-related metrics such as distance walked or run, calorie consumption, and in some cases heartbeat. It is a type of wearable computer. The term is now primarily used for smartwatches that are synced, in many cases wirelessly, to a computer or smartphone for long-term data tracking. There are also independent mobile and Facebook apps. Some evidence has found that the use of these type of devices results in less weight loss rather than more. Sleep tracker devices have a tendency to underdetect wakefulness. An activity tracker, also known as a fitness tracker, is a device or application for monitoring and tracking fitness-related metrics such as distance walked or run, calorie consumption, and in some cases heartbeat. It is a type of wearable computer. The term is now primarily used for smartwatches that are synced, in many cases wirelessly, to a computer or smartphone for long-term data tracking. There are also independent mobile and Facebook apps. Some evidence has found that the use of these type of devices results in less weight loss rather than more. Sleep tracker devices have a tendency to underdetect wakefulness. The term 'activity trackers' now primarily refers to wearable devices that monitor and record a person's fitness activity. The concept grew out of written logs that led to spreadsheet-style computer logs in which entries were made manually, such as that provided in the US by the President's Council on Physical Fitness and Sports as part of The President's Challenge. Improvements in technology in the late 20th and early 21st century allow automating the monitoring and recording of fitness activities and integrating them into more easily worn equipment. Early examples include wristwatch-sized bicycle computers that monitored speed, duration, distance, etc., available at least by the early 1990s. Wearable heart rate monitors for athletes were available in 1981. Wearable fitness tracking devices, including wireless heart rate monitoring that integrated with commercial-grade fitness equipment found in gyms, were available in consumer-grade electronics by at least the early 2000s. Electronic activity trackers are fundamentally upgraded versions of pedometers; in addition to counting steps, they use accelerometers and altimeters to calculate mileage, graph overall physical activity, calculate calorie expenditure, and in some cases also monitor and graph heart rate and quality of sleep. Some also include a silent alarm. Some newer models approach the US definition of a Class II medical monitor, and some manufacturers hope to eventually make them capable of alerting to a medical problem, although FDA approval would be required. Early versions such as the original Fitbit (2009), were worn clipped to the waist; formats have since diversified to include wristbands and armbands (smart bands) and smaller devices that can be clipped wherever preferred. Apple and Nike together developed the Nike+iPod, a sensor-equipped shoe that worked with an iPod Nano. In addition, logging apps exist for smartphones and Facebook; the Nike+ system now works without the shoe sensor, through the GPS unit in the phone. The Apple Watch and some other smart watches offer fitness tracker functions. In the US, BodyMedia has developed a disposable activity tracker to be worn for a week, which is aimed at medical and insurance providers and employers seeking to measure employees' fitness, and Jawbone's UP for Groups aggregates and anonymizes data from the company's wearable activity trackers and apps for employers. Other activity trackers are intended to monitor vital signs in the elderly, epileptics, and people with sleep disorders and alert a caregiver to a problem. Earbuds and headphones are a better location for measuring some data, including core body temperature; Valencell has developed sensor technology for new activity trackers that take their readings at the ear rather than the wrist, arm, or waist. Numerous companies have also released devices in the form of a ring that leverage the capillaries in the finger. There are collar-mounted activity trackers for dogs. Much of the appeal of activity trackers that makes them effective tools in increasing personal fitness comes from their making it into a game, and from the social dimension of sharing via social media and resulting rivalry. The device can serve as a means of identification with a community, which extends to broader participation. The standard activity-tracking smartphone or web apps present data in statistical form meant to be viewed after the activity has ended. However, research suggests that if we want a richer understanding of the data, we need intelligent computing to be included in the systems that run the apps. Some users and reviewers remain ambivalent towards the technology, making the point that in such a 'mirror' displaying one's identity, misrepresentations are problematic. All forms of lifelogging also carry privacy implications. Social networks associated with activity trackers have led to breaches of privacy such as involuntary publication of sexual activity, and the potential for advertisers and health insurers to access private health data through the devices is a concern.In 2016, there were several advances made in regard to fitness tracking geared toward kids with a variety of options from organizations such as UNICEF and Garmin.