You'll need to do some investigating into "how to figure out the activation status" ... it MIGHT be possible as a return of the SLUI type command-line tool for activation perhaps, or some such. I'm pretty sure there's bound to be "some way" for Windows to cough up "yes I am / no I am not activated".
Once that's known, script the relevant running / gathering, and throw the result into a simple registry value which you can then pick up as Custom Data as per normal.
So in essence:
- Script "running the command" + "massaging the output" (it may be "less than friendly") into something useful.
- Inject result into registry key.
- Pull registry key as normal with the inventory scanner as a piece of custom data.
But yeah ... I personally don't know (/haven't need to) find out whether a device is activated yet or not. Google-fu not being helpful (I'd be surprised if you'd be the first person in need of this snippet of info) ?