This is an idea for a Guard based Asset Pipeline for Laravel 4

config.php

<?php

return array(
  /*
	|--------------------------------------------------------------------------
	| Pipelines
	|--------------------------------------------------------------------------
	|
	| In this configuration, you will specify your asset pipelines,
	| For each pipeline you can specify what files you want included in
	| your final minified production file
	|
	*/
	'pipelines' => array(
		'application' => array(
			'styles' => array(
				'lib/bootstrap.css',
				'main.css'
			),
			'scripts' => array(
				'lib/jquery.js'
			)
		),
	),

	/*
	|--------------------------------------------------------------------------
	| The Path To Your Assets Directory
	|--------------------------------------------------------------------------
	|
	| Here, you'll specify where you want your assets directory to go.
	| This will be the base directory, where sass, less, and coffee directories
	| will be inserted.
	|
	*/
	'assets_path' => 'app/assets',

	/*
	|--------------------------------------------------------------------------
	| The Path To Your Coffeescript Assets
	|--------------------------------------------------------------------------
	|
	| This is an optional config in case you don't store your .coffee files
	| in $asset_path . '/coffee/'
	|
	*/
	// 'coffee_assets_path' => 'app/assets/coffee',
	
	/*
	|--------------------------------------------------------------------------
	| The Path To Your Less Assets
	|--------------------------------------------------------------------------
	|
	| This is an optional config in case you don't store your .less files
	| in $asset_path . '/less/'
	|
	*/
	// 'less_assets_path' => 'app/assets/less',
	
	/*
	|--------------------------------------------------------------------------
	| Your Compiled Assets Path
	|--------------------------------------------------------------------------
	|
	| This is the folder where your assets will be compiled to.
	| This is where all of your assets will compile to and should not be used
	| for minified production code.
	|
	*/
	'compile_dir' => 'public/src',

	/*
	|--------------------------------------------------------------------------
	| Your Compiled CSS Path
	|--------------------------------------------------------------------------
	|
	| This is an optional cofig in case you don't want your compiled CSS files
	| in $compile_dir . '/css/'
	|
	*/
	// 'css_compile_dir' => 'public/src/css',

	/*
	|--------------------------------------------------------------------------
	| Your Compiled JS Path
	|--------------------------------------------------------------------------
	|
	| This is an optional cofig in case you don't want your compiled JS files
	| in $compile_dir . '/js/'
	|
	*/
	// 'js_compile_dir' => 'public/src/js',

	/*
	|--------------------------------------------------------------------------
	| Your Production Folder
	|--------------------------------------------------------------------------
	|
	| This folder is the location where your minified and concatinated production
	| files will be placed
	|
	*/
	'production_dir' => 'public/assets',

	/*
	|--------------------------------------------------------------------------
	| Your Production CSS Folder
	|--------------------------------------------------------------------------
	|
	| This optional config specifies the folder where your minified and
	| concatinated CSS production files will be placed
	|
	*/
	'css_production_dir' => 'public/assets/css',

	/*
	|--------------------------------------------------------------------------
	| Your Production JS Folder
	|--------------------------------------------------------------------------
	|
	| This optional config specifies the folder where your minified and
	| concatinated JS production files will be placed
	|
	*/
	'js_production_dir' => 'public/assets/js',

);

File Tree

app/
|-assets/
| |-coffee/
| | |-main.coffe
| |-less/
| | |-main.less

public/
|-assets
| |-css
| | |-application.css
| |-js
| | |-application.js
|-src
| |-css
| | |-lib/
| | | |-bootstrap.css
| | |-main.css
| |-js
| | |-lib/
| | | |-jquery.js
| | |-main.js

Guardfile

guard :coffeescript, :input => "app/assets/coffee", :output => "public/src/js"

guard :less, :all_on_start => true, :all_on_start => false, :output => 'public/src/css' do
  watch(%r[^app/assets/less/(.+\.less)$])
end

guard :concat, :type => "css", :files => %w[lib/bootstrap main], :input_dir => "public/src/css", :output => "public/assets/css/application"

guard :concat, :type => "js", :files => %w[lib/jquery main], :input_dir => "public/src/js", :output => "public/src/js/application"

# Refresh the browser on save
guard 'livereload' do
  watch(%r{.+(?<!\.min)\.(css|html|js|blade\.php)$})
end

guard :phpunit, :all_on_start => false, :tests_path => 'app/tests/', :cli => '--colors -c phpunit.xml' do
  # Run any test in app/tests upon save.
  watch(%r{^.+Test\.php$})

  # When a view file is updated, run tests.
  # Tip: you probably only want to run your integration tests.
  watch(%r{app/views/.+\.php}) { Dir.glob('app/tests/**/*.php') }

  # When a file is edited, try to run its associated test.
  # Save app/models/User.php, and it will run app/tests/models/UserTest.php
  watch(%r{^app/(.+)/(.+)\.php$}) { |m| "app/tests/#{m[1]}/#{m[2]}Test.php"}
end

module ::Guard
  class Refresher < Guard
    def run_all
      # refresh
    end

    def run_on_additions(paths)
      refresh
    end

    def run_on_removals(paths)
      refresh
    end

    def refresh
      `php artisan guard:refresh`
    end
  end
end