Hi, currently the best option would be to detect the GameWindow size, which is the pixels on the device. We do not provide the size of the screen yet, but the resolution is also often sufficient. On iOS you can detect the device type based on its resolution (1024×768 or double the size is an iPad, otherwise an iPhone or iPod Touch).
In our newest update it will be possible to play for four persons on one device. Due to usability this should only be possible on tablets. The screen resolution is therefore not really sufficient. Best would be to get the information about the screen size in inch, so that I could say sth. like that