TotalTerminal for OS X provides a system-wide terminal window accessible via a hot-key, much like the console in Quake.
git clone --recursive git@github.com:binaryage/totalterminal.git
cd totalterminal
xcodebuild -workspace TotalTerminal.xcworkspace -scheme "TotalTerminal Package" -configuration Debug
When successfull. The TotalTerminal.osax is placed into ~/Library/ScriptingAdditions/TotalTerminal.osax.
To inject it into running Terminal.app use st alias (or rt alias is more convenient):
# put these into your bash profile: ~/.profile
alias kt='killall Terminal'
alias qt='osascript -e "tell application \"Terminal\" to quit" && killall -SIGINT TotalTerminalCrashWatcher'
alias st='osascript -e "tell application \"Terminal\" to «event BATTinit»"'
alias rt='qt ; sleep 1 ; st'
Alternatively you may use rake open to open Xcode workspace. Switch to "TotalTerminal Package" scheme and build from within the IDE.