A new Logstash input plugin called logstash-input-rets is now available to pull data out of MLS RETS servers (Real Estate Transaction Standard).
We're still working on a few kinks but the input is fully functional.
The input is available and documented here: https://github.com/consulthys/logstash-input-rets
PS: Thanks to the good folks at Estately for providing a pure Ruby library for interacting with RETS servers. For those interested, you can find it here: https://github.com/estately/rets