I've just submitted a pull request to you Rudy, based on Robin's code, to add the ability to compile all updated sass files. You then include your style sheets as you normally would, pointing to the generated .css file.
You can now either use the SassifyAll() function anywhere or head to the admin and click 'compile sass' to compile all your assets at once.
This is my first input to a Processwire Module so let me know if I've done anything wrong, or if I've stepped on anybody's toes!