They might seem fun at first, but when you start thinking about the day to day implications (security, charging, usability, waterproofness, wear&tear etc) most of these gadgets loose their shine. From the top of my head this ring costs around €99. Why would you buy it when smartphones and smartwatches are safer, easier to use, and already there?
Frankly as it stands currently these things seem to be more effective at getting press attention than actually solving anything.