I think these guys are most probably:
1) using software to tap onto the built-in or external antenna's hardware using its CLI
2) doing some FFT, DSP, ... number crunching
3) presenting everything with a nice GUI
There are projects out there like DD-WRT and a excellent 9 dB and 12 dB antennas from Linksys
I think 1) and 3) are just labor once you have the information and 2) has been been mathematically documented to exhaustion
How come OS projects similar to wi-spy haven't sprouted yet?
Am I missing something here?
Thanks lbrtchx