With Samsung wallet via the phone and a compatible car, think it only supports BMW, not sure if available for the watches.
@billbeu Seems it is not possible to use Digital Keys on Smartwatch at present, can only be use on one Galaxy phone. https://www.samsung.com/uk/support/apps-services/what-is-digital-key/
I do not work for Samsung or make Samsung Products but provide independent advice and valuable contributions.
My Device- S21 Ultra 5G ( SM-998B/DS ) CSC= BTU , 12GB/256GB
One Ui 5.0,Android 13 .