Fitness features Fitbit needs to add to new Zip, One and Surge trackers

Now that Fitbit updated its Charge HR fitness tracker with Charge 2 ($150 to $180), and its Flex with the new Flex 2 ($100), you have to wonder when we'll see a "Zip 2," a "One 2," or a new "Surge 2." And what cool features might the updated versions offer?Here are some highly subjective suggestions for future iterations of those three Fitbits. The suggestions aren't based on rumors, nor do I have any specific knowledge of Fitbit's plans, because company declined to provide insigh