https://www.youtube.com/watch?v=8mnd5qt63e8&list;=WL&index;=209

http://web.stanford.edu/~mkotaru/wicapture

I have been aware of machine learning projects that use RSSI (signal strength) (for example, try typing iwconfig in a linux terminal. You can grep that for signal strength.)

CSI (channel state information) is more though. Uses alternative firmware. Gets you phase sensitivity.

https://dhalperi.github.io/linux-80211n-csitool/index.html#external

mini PCIe is a pain. Many laptops support it and mini pcs. But still, that is a ~100$ investment or so.

plausible but unconfirmed alternative for atheros cards

http://pdcc.ntu.edu.sg/wands/Atheros/#PLT

Another paper describing localization

http://cs229.stanford.edu/proj2015/110_report.pdf

https://www.usenix.org/system/files/conference/nsdi16/nsdi16-paper-vasisht.pdf

https://www.youtube.com/watch?v=ZJrTVU_eajE