The features of tcpcontrol have been integrated into ucspi-tcp 0.80; the tcpcontrol package is provided here for use with old versions of ucspi-tcp.
tcpcontrol provides the same basic services as tcp-wrappers/tcpd provides for inetd: logging connections; rejecting connections from certain hosts; setting new environment variables for connections from certain hosts.
tcpcontrol is built for speed. Its rules are compiled into a hashed format with cdb, so you can easily deal with thousands of different hosts. It takes advantage of the TCP environment variables set up by tcpserver, so (unlike tcpd) it doesn't do any extra DNS or port 113 lookups.