Sundials: An ancient device known as a gnomon, a vertical pillar that measured the length of the sun’s shadow throughout the day, first appears in archeological records. Ancient Egyptians who also used large obelisks to track time, had made a more precise sundial, known as a shadow box, by 800 B.C.
Candle clocks: first referenced in a sixth-century Chinese poem and likely used before then, candle clocks burned down steadily, allowing time to be measured in wax segments.
Pendulum clock: Initially envisioned by Galileo Galilee, Dutch inventor Christian Huygens designed the first clock regulated by the swing of a pendulum.
H4 Marine Chronometer or “sea-watch”: John Harrison perfects his marine chronometer, allowing navigators to accurately determine their longitude at sea.
The Santos: Annoyed by always having to take his hands away from the controls while flying, Brazilian aviation pioneer Alberto Santos-Dumont asked a friend to design a bracelet attachment. The product was marketed and launched, and the modern wristwatch was born.
Dick Tracy's 2-Way Wrist Radio: The on-paper invention was inspired by wireless pioneer Al Gross and worn by Tracy and other members of the police force. The wristwatch was one of the comic strip’s icons and got an upgrade to two-Way Wrist TV in 1964.
Hamilton Watch Company’s Pulsar: The world’s first digital watch starts measuring time. Using an LED display that could only show hours, minutes and seconds, the watch was widely released in 1972 and made a splash after being strapped to James Bond’s wrist in Live and Let Die in 1973.
Casio C-80: A calculator watch that brought wrist-bound arithmetic to the mainstream. The basic plastic design cut the price tag of earlier designs while including the same functionality.
Seiko’s Data 2000: A watch, calculator and data input devise, Seiko’s design included a forearm-mounted keyboard “dock” used to enter text. The device could hold about 2,000 characters, transmitting data through electromagnetic coupling.
Timex Datalink: With enough memory to store around 50 phone numbers, memos or a list of appointments, the Microsoft-Timex joint venture was an early attempt to link computers to mobile devices. The watch used an optical sensor to wirelessly transfer data from a computer monitor flashing in a particular Morse-like pattern.
Linux Wristwatch: University of Toronto professor Steve Mann invented, designed, and built the world's first Linux wristwatch. When he presented the watch at an Institute of Electrical and Electronic Engineers event, he was named "the father of wearable computing." The watch had data, primitive video, and of course, time-keeping capabilities.
Samsung SPH-WP10: The world’s first commercial watch phone, it was at the time the smallest and lightest wireless terminal ever made. It offered about 90 minutes of call time, contacts list capabilities, and vibration call-alert.
The Fossil Wrist PDA: With a stylus integrated into the wristband, Fossil’s watch included two megabytes of memory, a rechargeable battery. Address book, to-do list, memo and calculator features came standard. It featured a 160x160 pixel display.
Garmin Forerunner: The first step in wearable wellness, Garmin used GPS to enable users to track distance traveled, speed, pace and calories burned.
Microsoft SPOT Watch: for a brief time in the ‘00s Microsoft was interested in FM-radio waves. Its Smart Personal Object Technology (SPOT) enabled watch was able to relay bits of up-to-date information about weather, news, sports scores and stock quotes.
Samsung S9110 Watch Phone: Featuring the thinnest-to-date 11.98-millimetre panel and a 45-millimetre colour LCD display, the watch offered e-mail capability, a music player and a speakerphone.
inPulse Smartwatch: The future Pebble designer Eric Migicovsky's company, known as Allerta at that time, launched a Blackberry watch capable of receiving emails, running Blackberry Messenger and displaying caller ID.
Pebble Smartwatch: Migicovsky broke Kickstarter records with a pitch for the Pebble smartwatch. He raised $10.2-million, and most of his 70,000 backers also ordered a watch as part of their support.
Android Wear: Google announces an operating system designed specifically for smartwatches and other wearables. Android Wear launched with the Motorola Moto 360 and the LG G Watch.