How to add Service to Finder Toolbar
You can create an application doing exactly this using ScriptEditor.app and then add it to Finder Toolbar.

First place this line inside your ~/.bash_profile file: 

alias cdf="eval \"cd \\\"\\\`osascript -e 'tell app \\\\\\\"Finder\\\\\\\" to return the POSIX path of (target of window 1 as alias)'\\\`\\\"\""


This will change the active directory to the one of the topmost Finder window.

Then create an application in ScriptEditor.app like:

tell application "Terminal"
    do script "cdf"
    activate
end tell


Save this as an application and add it to the Toolbar with ⌘ CMD + Drag.