The matlab serial object can be used to connect to external devices that use serial communication, such as microcontrollers, GPS receivers, heartrate monitors, etc. In order to use a serial object, you need to know the serial port name.
GET_PORT_LIST returns a list of serial port names which are suitable for connections with serial port objects. The function is cross-platform (OS X, Linux, Windows) and does not require any Matlab toolboxes.
Example: (on OS X)

devices = get_port_list;
disp(devices)
'A700elGZ' '/dev/tty.usbserial-A700elGZ'
'PXFARNQU' '/dev/tty.usbserial-PXFARNQU'
Example: (on Windows)

devices = get_port_list;
disp(devices)
'6' 'COM6'
'1' 'COM1'
device_connection = serial(devices{1,2});
fopen(device_connection);
% send/receive data, etc
fclose(device_connection);