1. A method comprising: initiating, by a first Bluetooth device, connection establishment with a second Bluetooth device; carrying out a service discovery procedure by the first Bluetooth device with the second Bluetooth device, during which the first Bluetooth device receives from the second Bluetooth device a broadcasted radio frequency discovery frame comprising at least one unique service identifier that advertises and uniquely identifies a personal training data service, wherein the personal training data service is provided by the second Bluetooth device and processes at least one personal training data item that represents personal training data associated with a user during a physical exercise; and transmitting, after the service discovery procedure, at least one radio frequency frame by the first Bluetooth device to the second Bluetooth device, wherein the at least one radio frequency frame comprises an information element specifying personal training data associated with the user of the discovered personal training data service and a command information element specifying how to process the personal training data specified by the information element associated with the at least one radio frequency frame.