The health and safety protocols for major league baseball in 2021 are out, and they include a bit of big brother monitoring (emphasis added):

Under the agreement, COVID-19 testing has been expanded and includes voluntary testing for family and household members of covered individuals. Players will wear contract tracing devices in team facilities, during travel and workouts. Masks are required to be worn while in team facilities and dugout. Each team will have a “Facemask Enforcement Officer” to best ensure compliance. Mental health and well-being resources will be provided to players and staff throughout the season.

AJC.com

This may be similar to app you can run on your phone that tell you if you got close to someone who reported a positive COVID-19 test. I don’t know if during travel means constantly while on a road trip or just when the teams is moving together. Maybe it’s designed to catch players leaving hotels when they should be staying put.