New Delhi, Jan. 26 -- The Australian Open 2026 is underway. Apart from the tennis tournament and players' prowess, what has got everyone talking is a device which Carlos Alcaraz, Jannik Sinner, Aryna Sabalenka wore, but were asked to remove before their matches.

Jannik Sinner was wearing the device under his wristband, but umpire Allensworth spotted it as the players came to the net for the pre-match coin toss, reported The Independent.

The device in question is a Whoop wristband - a fitness tracker which can measure fitness and biometric data, including heart rate and body stress - which can also provide insights into recovery. Tracking technology can help monitor a person's sleep, strain, stress and heart health.

Experts say wearable...