I had this idea years ago and it seems like a good idea but there wouldn't be a very large market for such a device.
My guess is that R&D on something like that,with such a limited market, would put it at a price on par with the sophisticated meters all already out there.
The USB port itself couldn't supply enough power for the lnbf
I'm not to sure I would want to drag my laptop up to the roof anyway.
Now plugin a laptop into a birddog or sat buddy type meter and getting real time data ... now your talking.