If you want to keep track of your workout, a sport watch is a great choice. It weighs 82 g. Use the built-in heart rate monitor to keep track of your training progress.
From OnBuy
Garmin fenix 6X Pro Solar Edition Watch titanium carbon grey - Multicoloured
Watch Shop
Garmin fenix 6X Pro Solar Smartwatch - LCD / Silver
This product is also available at 1 unverified merchant.