Connect different mobiles devices to allow custom accent marker/highlight settings

Either have a way for joining a session where start/stop/tempo changes are synced for multiple devices, and/or allow setting different beat/highlight settings per device. Drummer might want different config from guitarist. Basically independent control of how the beats are played per device, synced tempo and start/stop. Controlled from one phone is ideal, but joining a session would work too. Should be able to be saved as a song with config for each device remembered.