Systems and methods for automatic detection and signaling of an on-line status of a headset or other audio transmit/receive system used with telephony and/or other multimedia application software running on personal computers or other processor-based hosts are disclosed. The system generally includes a headset to communicate with the host executing the application software such as a softphone utilizing the headset via a port of the host, an on-line status detector in communication with the host via the port to detect the on-line status based on detecting a request for transmit data at the port and based on a signaling protocol associated with the port and independent of the application software, and an on-line indicator selectively activated by the on-line status detector. The request for transmit data may be detected by the opening or presence of a transmit channel opened by the host on the port.