it's fairly simple to get getty running to listen for a connection on the serial port
we have a line in our /etc/inittab that says:
co:2345:respawn:/sbin/agetty -L ttyS0 19200 vt100
so on each normal runlevel we listen on ttyS0 (COM1) at 19200 baud using vt100 terminal emulation. you can just run the command directly - i.e. "/sbin/agetty -L ..." but each disconnection will terminate the process. so by having the inittab entry it will reconnect. and of course as this is linux, you don't need to reboot for this at all. you will however need to reread the inittab file to make the settings take effect - just run "init q" according to the manpage for init. before you do that though, ensure that the getty command is more than happy to run as you want as you could come unstuck if you break inittab. alternatively you could use a cruder cop-out and add a cronjob to start getty if it's not already running. bit shabby but potentially safer.