Screw you, Ruby. I'm doing it with node.js. ;) Watch for file changes in .scss files and compile them with sass. Read here, why: https://plus.google.com/109651506622355695262/posts/eCSwytEr2cW

sass-watchr

var watchr         = require('watchr'),
    exec           = require('child_process').exec,
    isCompiling    = false,
    needsRecompile = false;

console.log('started watching sass files for changes...');

watchr.watch({
    path: './scss',
    preferredMethods: ['watchFile', 'watch'],
    listener: changeListener
});


function changeListener(type, filePath) {
    if (filePath.indexOf('.scss') > -1) {
        console.log('sass file changed', filePath);
        if (!isCompiling) {
            isCompiling = true;
            needsRecompile = false;
            runSass(function () {
                isCompiling = false;
                console.log('Sass file compiled.');
                notify('Sass file compiled.');
                if (needsRecompile) {
                    changeListener(type, filePath);
                }
            });
        } else {
            needsRecompile = true;
        }
    }
}


function runSass(done) {
    var sass = exec('sass scss/main.scss:scss/main.css', function (err, stdout, stderr) {
        if (err) {
            console.warn(err);
            process.exit(1);
        }
        if (typeof done === 'function') { done(); }
    });
}

function notify(text) {
    var notification = exec('notify-send "' + text + '"');
}