helm-demo.el

(setq demo-options
      '("Stuff"
        "things"
        ("Custom" . (lambda () (read-from-minibuffer "Custom: ")))))

(defun demo-select (el)
  (cond
   ((functionp el)
    (funcall el))
   (t
    el)))

(defun demo-edit (el)
  el)

(setq demo-actions '(("Select" . demo-select)
                     ("Edit" . demo-edit)))

(setq helm-demo-source
      '((name . "Demo")
        (candidates . demo-options)
        (action . demo-actions)))

(defun run-demo ()
  (interactive)
  (let ((result (helm :sources '(helm-demo-source))))
    (if (not result)
        (error "helm returned nil :(")
      (message "Got: %s" result))))