A portlet as it is no. Remember that is a web component and it needs a browser, the context of a portal and lots of things...
With the mobile SDK you can call your Liferay backend from your app and access the Liferay Portal remote services or your own (with the builder) through JSON web services.
With Liferay Screens you can use pre-made components for mobile phones (like portlets for native apps) or roll your own.
