SFM Custom Actions of type URL can be used for launching external websites / custom VF pages. They are indicated by Webservices icon in the Actions menu, and are supported only when you are online. Tapping them launches the configured URL in the device's browser window. If the configured URL is a path to a VF page in your Salesforce org, it will open your org in the device's browser window. Upon logging in, it will navigate to the configured VF page.