sample-grunt.js

grunt.event.on('watch', function (action, path, target) {
	if (target === 'html' || target === 'css' /* and on and on for your target types in watch */) {
    grunt.config(['clean', 'any'], []);
    // Making an assumption your using sftp and have a current working directory setup
	  cwd = grunt.config.get(['sftp', 'cwd']) + '/';
	  path = path.replace(cwd, '');
	  grunt.config(['sftp', 'options', 'path'], path);
  }
});