Command to launch genymotion headless - 

• if player is not already added to path, add it to path using below command in your ~/.bash_profile

When more than one device is connect use ‘adb -s‘ is used to redirect commands to particular device
Once emulator is running they will be listed under adb devices
Example: 

      
Verfiy command are send to correct device:
 Send command to click on menu key on android device when multiple devices are connected