Whoop reads recovery and strain and turns it into coaching. The Fitbit Air covers the broader daily picture inside the Fitbit app.
People who trust one for sleep and the other for activity, or who are comparing both before committing, end up wearing two bands. Smartlet carries both on a single wrist instead.
Smartlet replaces your mechanical watch strap via the standard spring-bar system. Classic, Shadow, or Titanium. No tools required.
Smartlet uses a dedicated adapter or native lug pins depending on your smartwatch. The connector snaps onto the Smartlet module. Zero modification to the mechanical watch.
Both watches sit on the same wrist. All smartwatch sensors maintain direct skin contact and operate normally.