gulp-less + watch

gistfile1.js

var less = require('gulp-less');

gulp.task('less', function() {
  gulp.src('./home-of-less-files/**/*.less')
    .pipe(less({))
    .pipe(gulp.dest('./destination-directory'));
});

gulp.task('watch', function() {
    gulp.watch('./home-of-less-files/**/*.less', ['less']);
});