We use the various device fields for either IOS or Android as a filter point in conjunction with OS and we also use a URL/Path that we know differs for our mobile apps/services.

Another option, could be for your system to capture local device info (like Current OS/Device) and send that over as a custom attribute.

As there is no current device data point, it takes a bit of play to get it right for your system design.

Hope that helps.