Why the wrist
The wrist is a convenient place for a gadget. It is easy to glance at, close to the skin for sensing, and already accepted socially thanks to watches. For centuries, the watch was a small mechanical device that told time. Electronics changed what it could do, and the story of wearable devices is largely a story of adding features while keeping the watch small and comfortable.
Electronic watches and wrist gadgets
Quartz watches that used a vibrating crystal for accuracy spread in the 1970s, and digital displays soon followed. Early LED digital watches in the first half of the decade were novelties that required a button press to show the time. Liquid crystal displays, which use far less power, then became common.
Manufacturers began adding functions. Through the late 1970s and 1980s, watches included calculators, alarms, stopwatches, timers and games. Some models offered small memory banks for phone numbers or notes, which suited the era of paper address books. Other watches experimented with data transfer from computers, using methods such as light patterns from a screen or cables. These products are sometimes called the ancestors of smartwatches, but they worked alone and could not connect to the internet.
Early sensing: steps and heartbeats
A parallel line of development used sensors to measure the body. Mechanical step counters had been around for a long time, and in Japan, pedometers were popular from the 1960s, which is often linked to the well-known goal of 10,000 steps a day. That number began as a catchy target rather than a medical threshold, and current health advice does not treat it as a magic figure.
In the early 1980s, a Finnish company introduced a wireless heart rate monitor with a chest strap that transmitted to a wrist receiver, making heart rate monitoring practical for athletes. Sport watches with built-in timers, altimeters and compasses followed for hikers and divers. The addition of GPS positioning chips in the 2000s let runners and cyclists record routes and distances.
Smartwatches before the smartphone era
Some companies in the 1990s and 2000s tried watches that received information such as news, weather or calendar alerts, often through radio broadcast or by connecting to a computer. Others built watches that ran their own small programs or paired with early Bluetooth phones. These efforts were interesting but limited: the screens were small, the batteries drained quickly and there was little content to show. Few people bought them.
Fitness bands and the connected era
The mid-2000s to early 2010s brought a different approach. Instead of trying to be a tiny computer, fitness trackers did a few things well: they counted steps using accelerometers, estimated sleep and synced the data to a phone app or website. Small, light bands with simple displays or none at all made this affordable and comfortable. One company’s clip-on and wrist trackers, launched around 2009, helped bring them to a wide audience.
Meanwhile, smartphones created the missing infrastructure. A phone supplied the internet connection, app ecosystem and a large screen for settings. Bluetooth Low Energy, a wireless standard designed for small, power-sparing devices, let a watch stay connected without draining its battery in hours. Crowdfunding and technology companies launched smartwatches that showed notifications from the phone. A crowdfunded watch with a low-power display made headlines in 2012, and major phone makers released their own models in 2013 and the years after. Apple’s smartwatch arrived in 2015.
What modern smartwatches added
Later generations added touchscreens, cellular radios, contactless payments, voice assistants and more sensors. Optical sensors on the underside estimate heart rate by detecting changes in light reflected from blood flow in the skin. Some devices can record an electrocardiogram-style tracing or flag irregular heart rhythms, although these features are intended for screening or information and do not replace a clinician’s diagnosis. Readers interested in the wider health context can see our articles on wearable health monitoring and remote monitoring.
Why the progress was slow
Several constraints shaped the pace. Batteries had to fit in a very small space, so early designs gave up features for endurance, and improvements in lithium-ion batteries and low-power semiconductor chips were essential. Screens had to remain readable in daylight. The devices needed to be water-resistant and comfortable all day. And, until phones were widespread, a watch had little to connect to.
Open questions
Wearables raise questions about data. Sensor readings about activity, sleep and location are sensitive, and people may want to check how a company stores or shares them, a topic related to online privacy. Accuracy also varies between devices and conditions, so numbers such as calories burned should be seen as estimates. These issues will probably remain part of the conversation as the devices improve.