This is a Sublime Text 2 package that will run Pyflakes against Python files being edited and highlight the warnings returned.
The package requires Pyflakes to already be installed and in a place where Python can find it, e.g. /usr/bin
Install Pyflakes and set Python Path in SYSTEM PATH
Just drop pyflakes.py into Sublime Text 2/Packages/User. The package will run every time a Python file is saved.