The 1977 HP-01 digital calculator was arguably the very first smart-watch to hit the market nearly 38 years before the Apple Watch. The watch was a marvel for its time. Not only could it perform basic calculations, the watch could do dynamic time and date calculations, algebra, and even function as a stopwatch and alarm clock. The watch in perfect condition can be found on eBay from time-to-time, for a price ranging up to $14 500 on eBay.
