homebrew.mxcl.bitlbee.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC
        "-//Apple//DTD PLIST 1.0//EN"
        "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>Label</key>
<string>homebrew.mxcl.bitlbee</string>
<key>ProgramArguments</key>
<array>
  <string>/usr/local/sbin/bitlbee</string>
  <string>-I</string>
  <string>-n</string>
</array>
<key>Sockets</key>
<dict>
  <key>Listeners</key>
  <dict>
    <key>SockNodeName</key>
    <string>127.0.0.1</string>
    <key>SockServiceName</key>
    <string>6667</string>
  </dict>
</dict>
<key>inetdCompatibility</key>
<dict>
  <key>Wait</key>
  <false/>
</dict>
</dict>
</plist>

install.sh

# brew install bitlbee --with-libpurple --with-libotr
cd ~/Library/LaunchAgents/
wget https://gist.github.com/cstrahan/5146621/raw/d3ab3317a81ce265de5d7eb3adb7e9fbaea80d65/homebrew.mxcl.bitlbee.plist
launchctl load -w ~/Library/LaunchAgents/homebrew.mxcl.bitlbee.plist
launchctl start homebrew.mxcl.bitlbee

You sir are now my personal hero! I've been banging my head against the monitor trying to work out how to do this for ages, excellent work that man. :-)