While the arduino prints serial information fine once it's been "connected" (like by opening serial monitor or by pressing the connect button in CoolTerm), the arduino does not establish a connection or send data through serial when connected to another device. In this case, when I plug a device (TinyTrak3+) which can only receive serial data to the arduino, it doesn't receive any data from the serial. Is there any way to force the arduino to actively send through the serial port regardless of whether it feels a "connection" has been made?
It is impedance problem on serial port if the second device is connected. Simply the load on port is too high so the signal is damaged. Partial solution could be 1k resistor in series on each line. Mechanical or electronic switch is better solution.
Problem with electronic switch is a switching signal. My Arduino clone has DTR and RTS on header and can be used for such purpose - connect/disconnect from terminal switch the serial port to the device vice versa off/on.