For completeness, here is also a related discussion, in which I proposed a PSK31-based approach (which could use the actual SSB frequency).
RTTY would also be an option. As the KX2 has PSK31 built-in, this could become a very handy solution for KX2 users.
We would need PSK31 skimmers, but RBN already has them:
http://www.reversebeacon.net/dxsd1/dxsd1.php?f=116
The same would work for RTTY, but that might require a tablet or smartphone + soundmodem cable.
The main challenge would then be to determine whether such a PSK31 or RTTY CQ is actually for SSB. If the RBN telnet data includes the string of the call, a simple “/SSB” or “SSB” could be defined for such CQ calls.
That would require minimal additional effort and you could suddenly use the wide coverage of HF to spot you. And you could try to use a simple audio recording of a PSK31 or RTTY CQ call and play it back.
73 de Martin, DK3IT