You can use file options to specify that a script run each time the file is opened. This script can detect the device being used and then select the starting layout appropriate for that device. Navigation buttons, scripts, menus on that layout can then limit the user to only those layouts appropriate for their device.
Get ( ApplicationVersion ) can be used in this script to identify the device. See this knowledgebase for more details: http://help.filemaker.com/app/answers/detail/a_id/7734/kw/Get%28ApplicationVersion%29