OK, I got a clear view of that situation yesterday. What is the state of
the passive Atheros code.
My understanding is that it is very early alpha right now. Passive-capable Atheros code is under development for Linux (and presumably other freely available OSes, such as FreeBSD), and Mick is/was working with those teams to bring that over to KisMac and MacOS X. But I don't recall them having gotten very far.
Then I should ask a colleague in our electronics department to glue together something with a well documented chipset. He has done that already with 802.11b stuff for an embedded device.
You can glue together anything you want. But where would you get the drivers?