Many people wonder how to switch devices without losing the data of the day such as the steps they may have accumulated. The current wisdom is to switch devices at the very start of the day. This comes up when you want to initiate a newly purchased device or other times when it is inconvenient to continue to use the current device.
For example, someone might have a vivoactive or a vivosmart and an old vivofit sitting in a drawer that probably rarely gets used but is considered a backup. Since the vivoactive/vivosmart will eventually need to be recharged for a couple of hours, there is no real way to count steps while it's in a charger. It seems to me that it would be useful to sync the device to be charged to Connect and then have the ability to transfer accumulated steps/calories/distance/goals etc. of the day to the backup device.
In other words, the feature would be to have the ability to transfer data for the day from one device to another through Connect.