[frankacter]

>I bought a Wifi scale specifically so I don't have to have my phone with bluetooth on, nearby.

Our has that option, but as multiple people in the house used the scale, having a phone on hand (which we do anyway) streamlines the process versus having to identify the user weighing.. user preference really.

>Does the BT-connection open the app itself, or just initiate a sync in a background service?

Background service as best as I can tell. I rarely, if ever, open the app in foreground and the weight is captured.