Tablet!
I am surprised we don't have a tablet icon yet. There is a family of tablet out there for different OS, such as iPad, Win 8 tablets and Android tablets; then there are mini tabs and large phones. These icons would be welcome. It would also help to have a generic mobile device icon without a mention of the OS, something that can be used to symbolize mobile devices in general, not a particular brand or OS.
1) indicating that an app is designed to runs on all types of devices:
2) indicating that an app is designed only for mobile phones or tablets
3) indicating that an app is designed to work with at least two or more mobiles/tablets (e.g. games that can only be played by two or more persons).