Apple (AAPL) shipped 4.2 million Watches in the second quarter, becoming the top vendor of wearable bands in the world, according to estimates by Canalys. Despite the Apple Watch's higher price tag, Canalys said the device easily overtook all other smart watch vendors, including Fitbit (FIT). Overall, sales would have been even higher if Apple had not missed the 2014 holiday selling season or experienced supply constraints that stalled shipments for the first couple of months after the device's launch, Canalys said. The smart watch is still in its early days on the market, and Canalys vice president and principal analyst Chris Jones noted important improvements needed to make it a hit. He said in a statement, 'Improvements in performance, battery life and sensor integration are needed to make future models more attractive, but it is the quality of third-party apps that will determine whether the Apple Watch will be a long-term success.'