In our Pugpig app containers you can set HTML classes to be injected into the <body> of your page HTML.
To do this add "Body Class" key to you Config.plist with a string value for your class
<key>Body Class</key> <string>awesome</string>
This will add a script to the bottom of each HTML which has
This can be used for various requirements including showing different content on iOS app and Android apps e.g specific Help pages. This isn't the ability to set classes that are device or OS specific however it does give you the ability to set app level classes for different platforms.