In the past week, a few companies with wristworn activity tracking devices, Withings, Xiaomi, Jawbone, and Misfit, have announced new features or accessories for their trackers.
Last week, Jawbone announced that the UP4, which was first announced in April, is now available and shipping in the US from the company's website. The UP4, which costs $199, has an American Express NFC-enabled payment...
