Xiaomi has yet to expand most of its mobile products to the US market, but it had an unexpected hit on its hands with the competitively priced (and globally available) Mi Band fitness tracker. The $15 device shipped more than 20 million units, and now the follow up Mi Band 2 is official after being shown off a few weeks ago. It's a little more expensive than the last one (RMB 149 or $23), but it has some nice upgrades.

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