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This SDR implementation looked really interesting for sniffing monitor output - https://github.com/martinmarinov/TempestSDR

Alas I don't have a suitable SDR to try it with.

Holy crap, it works for distances up to 120m using a custom built antenna. https://youtu.be/8HV70b-DpE0?t=23m46s

Though $50 will get you enough of an antenna, amp and SDR to get started...