Viewing (monitoring) line status of a serial port

Is there a utility software (or an easy method to do it from shell script) to display a serial port’s status — i. e. blinking “RXD”, “TXD”, “DCD”, “DTR”, “DSR”, “RTS”, “CTS”? Particularly, I need to monitor whether “DCD” line is set most of the time and momentarily cleared on some interval. The port doesn’t need to be sniffed, it’s okay to open it exclusively.

In DOS and Windows world, it’s usual for terminal emulator and other modem-related software to display pin status, either in GUI or in console applications. However, I couldn’t find an alternative even for Linux (although some say it may be possible to examine /proc/tty/driver/serial by hand, if it exists), not to mention FreeBSD, which is my actual target. Common tools like cu and minicom only display port settings at most, not the status.