The topic Fitbit Air has status light & double-tap gesture, gets Whoop size comparison is currently the subject of lively discussion — readers and analysts are keeping a close eye on developments.
This is taking place in a dynamic environment: companies’ decisions and competitors’ reactions can quickly change the picture.
The hardware design of the Fitbit Air is quite straightforward, but there are two features that aren’t particularly obvious until you start wearing the wearable.

All the hardware is housed in what Google refers to as the “pebble.” (Note: This is not the first time Fitbit has used that name for the core component of its fitness trackers.)
The left edge of this pebble has a status light, with bands featuring a hole for it to shine through. As such, there is a specific orientation you have to keep in mind when changing straps (emphasis ours):

Firmly double tap the top of the tracker to confirm you can see the LED light flash.
“Firmly” double-tapping the Fitbit Air wakes the status light:
That gesture is also used to silence Smart Wake and one-off alarms that you set inside the Google Health app.
Meanwhile, Fitbit Air demo units are already in the ten US Google Stores, including the newest location that opened on Friday, which has led to size comparisons with Whoop. Google’s hardware is noticeably narrower.