Since the Persee Color/RGB camera is only 1280x720, I wonder if it's possible to add an extra camera through USB so I can have a better quality video output on my Unity application.
I don't see a reason why not. You can stream many UVC camera feeds connected to Unity at the same time. Limitations would be bandwidth and hardware related.
You could try with a regular Webcam plugged into another USB port.
I was actually considering connecting the camera to TVico [Orbbec Persee] and use this external camera feed and Persee tracking combined.
But I'm guessing connecting a usb webcam on the TVico USB port won't do anything?
Hum so you have unity installed on Orbbec Persee?
Not Unity, but I have an APK installed which was generated through Unity