ftpd has a command-line flag `-u` that writes logins to /var/run/utmp which supposedly makes logged in users visible to commands like `who`. (compare with -U which turns this off, the default).
Implement that by editing /etc/xinetd.d/ftp's server-args line.
As for a nice pretty GUI wrapper, I don't know of any but I'd be very surprised if you couldn't find something on VT...even if it's an FTP server itself.