The lack of a native power reading on the vivoactive is very disappointing given how much of the early marketing hype mentioned this as a feature. I suspect a connectIQ third party workaround isn't really gonna cut it for most if their need is anything like mine. I want to capture power within the cycle app so that it transfers with the rest of my ride data to update my strava account with full ride data all within the ride file. Don't see how this can happen without Garmin adding the ANT+ power sensor as a selectable option for a cycle workout.
Just discovered this app:
https://apps.garmin.com/en-US/apps/38e4c506-b192-4d45-968a-38850c3dfd85
I have not tried it on an actual bike ride yet, but can confirm that I'm able to connect to a Quarq powermeter and the watch will show both watt and cad data.
Hence it is possible for the Vivoactive to connect to an ANT+ powermeter and show data. Recording the data is another matter, but it should be possible.
Update: Tried the app today for a very short testride: It do show Watt data, but only very briefly as it alternates between showing some data above zero followed by showing zero and then some watts above zero. It is mentioned that the app was developed for testing purpose using a Rotor powermeter, hence it could be the reason for the alternating watt values because the Rotor powermeter has a separate right and left recording sensor whereas my Quarq powermeter has not and only meassures power in the right arm spider. The very short positive watt data shown looks similar to the values recorded on my Garmin computer :-)