Fitbit announced it has shipped over one million each of its Blaze and Alta activity trackers less than a month after their debut, leading to a 13 percent surge in the mid-day trading of Fitbit shares on March 31. The Blaze smart fitness watch, retailing at $200, is now the top-selling device in Amazon's watch and heart monitor categories, despite a lukewarm reception by some attendees at the Consumer Electronics Show in Las Vegas in January. The cheaper Alta fitness wristband hit one million in sales after just three weeks on the market

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