Smartwatch

A smartwatch is a wrist-worn computing device combining timekeeping with health monitoring, smartphone notifications, app functionality, and wireless connectivity. Running watchOS, Wear OS, or proprietary operating systems, smartwatches pair with a smartphone to extend its functionality to the wrist. The Apple Watch, launched in 2015, dominates the category and has become the world’s best-selling watch of any kind — mechanical or electronic.

A smartwatch has a square, rectangular, or round watch case — typically 40 to 49mm in diameter or width — housing a colour touchscreen display. The case is aluminium, stainless steel, or titanium on premium models, polycarbonate on budget devices. Case thickness runs 10 to 13mm. A digital crown or physical button on the right edge provides navigation input supplementing touchscreen interaction.

The watch face is fully customisable — displaying analogue or digital time, health data, weather, calendar, and app information in user-configured layouts called watch faces or complications. The display is always-on at reduced brightness on premium models or activates on wrist raise. Sapphire crystal glass covers the display on premium tiers; Ion-X glass on standard models.

Interchangeable straps attach via quick-release pins or proprietary connectors. Standard strap widths are 20mm, 22mm, or Apple Watch’s proprietary 38/40/41/44/45/49mm sizing. Straps are silicone, fluoroelastomer, woven nylon, leather, stainless steel, or titanium. Sensors on the case rear — optical heart rate sensor, ECG electrodes, blood oxygen sensor — appear as circular windows against the case back.

Brand identification: Apple Watch has a square case with rounded corners and a proprietary side button plus digital crown. Samsung Galaxy Watch uses a round case. Garmin uses round or rectangular cases with a more functional, multi-button design language oriented toward sport.

A smartwatch tells the time, monitors heart rate continuously, tracks steps, distance, calories, sleep quality, blood oxygen saturation, and on some models ECG and blood glucose. It displays smartphone notifications — calls, messages, emails, app alerts — and allows limited responses from the wrist. It provides GPS navigation for running, cycling, and hiking. It processes contactless payments via NFC. It controls music playback and smart home devices. On cellular-enabled models it makes and receives calls and messages independently of a paired smartphone.

1. An ARM-based processor runs the watch operating system and applications, optimised for low power consumption to extend battery life.
2. The optical heart rate sensor uses green LED light and a photodiode — blood absorbs green light, so the sensor measures the variation in light reflection caused by each heartbeat through the skin.
3. The accelerometer and gyroscope detect wrist movement, step cadence, and activity type for fitness tracking.
4. GPS receivers on sport-oriented models triangulate position from satellite signals for route and distance tracking.
5. Bluetooth connects the watch to a paired smartphone for notification sync, app data, and phone calls. Wi-Fi and cellular radios on premium models provide independent connectivity.
6. A lithium-ion battery — typically 200 to 500mAh — provides 18 hours to two weeks of use depending on features enabled and model.

Calculator watches and early digital watch-computers appeared from the late 1970s — Seiko’s Data 2000 in 1983 could store memos and phone numbers. Microsoft’s SPOT (Smart Personal Objects Technology) platform launched smartwatches with MSN Direct data services in 2004 but failed to achieve consumer traction. Samsung released an early smartwatch in 1999 that could receive email — the SPH-WP10 — but it was too early for the supporting ecosystem.

The modern smartwatch era began with Pebble, which launched via Kickstarter in 2012 raising $10.3 million — then a record. Pebble used an e-paper display for long battery life and connected to iPhone and Android via Bluetooth. It sold over 2 million units before being acquired by Fitbit in 2016.

Apple Watch launched on April 24, 2015 after being announced by Tim Cook in September 2014. It sold an estimated 4.2 million units in its first quarter, immediately making Apple the world’s largest watch manufacturer by revenue. Apple Watch Series 4 in 2018 added ECG capability — the first FDA-cleared ECG on a consumer wearable — and has been credited with detecting previously undiagnosed atrial fibrillation in thousands of users.

The global smartwatch market exceeded 100 million units annually by the early 2020s. Apple holds approximately 30% market share, followed by Samsung, Garmin, Huawei, and Fitbit. Health and medical monitoring capabilities continue to expand with each generation — blood glucose monitoring without finger-stick testing is expected to arrive in consumer smartwatches within the mid-2020s.

• Apple Stores and electronics retailers for Apple Watch
• Samsung, Garmin, and Fitbit retail and online channels for alternatives
• Telecommunications carriers bundling smartwatches with phone plans
• Secondhand via eBay and Facebook Marketplace — battery condition is the key variable
• Thrift stores occasionally for older Fitbit and early generation models

Fitness tracker: A wrist-worn health monitoring band without a full touchscreen display or app platform. Distinguished by its elongated band form, minimal or no display, and focus on step counting, heart rate, and sleep tracking without the broader computing functionality of a smartwatch. Fitbit Charge and Xiaomi Mi Band are fitness trackers rather than smartwatches.

Hybrid smartwatch: A traditional analogue watch with hidden smart features — step tracking, notification alerts via hand movement — but no touchscreen display. Distinguished by its traditional mechanical watch appearance and the absence of a colour screen.

GPS sport watch: A purpose-built GPS device for running, cycling, or triathlon with limited notification features. Garmin Forerunner and Fenix series devices straddle the line between GPS sport watch and smartwatch and are marketed as both.

Smartwatches depreciate rapidly and battery degradation makes older models less desirable. Apple Watch holds value best.

• Apple Watch Series 10 new: $399—$799
• Apple Watch Ultra 2 new: $799—$999
• Apple Watch two generations old in excellent condition: $150—$250
• Apple Watch four or more generations old: $50—$120
• Samsung Galaxy Watch current generation new: $249—$649
• Original Apple Watch (2015) as collectible: $30—$80 working

Battery service is the primary consideration on used smartwatches — batteries typically degrade to 80% capacity within 500 charge cycles. Apple offers battery replacement for Apple Watch; third-party service exists but is complex due to the sealed waterproof construction.

Smart rings — the Oura Ring being the most prominent — provide health monitoring without a wrist display. Earbuds with health sensors embed heart rate and activity monitoring in audio devices. Traditional mechanical watches remain the prestige alternative for those who prefer pure horology without computing functions. No category has emerged to displace the smartwatch as the dominant wrist-worn computing and health platform and the market continues to grow driven by expanding medical monitoring capabilities.

Looking for one? Where to buy a Smartwatch →

Looking for one? Where to buy a Smartwatch →

• Square, round, or rectangular watch case 40 to 49mm
• Colour touchscreen display — always-on or raise-to-wake
• Digital crown or physical button on right edge
• Interchangeable straps via quick-release or proprietary connector
• Optical sensor array on case rear for heart rate and health monitoring
• Charging via magnetic puck or proprietary dock — no physical port
• Brand: Apple Watch, Samsung Galaxy Watch, Garmin, Fitbit, or Huawei
• Pairs with iPhone (Apple Watch) or Android/iPhone (most others) via Bluetooth