Off-chain, centralized and trustless (*) payment channel for high frequency trading between two peers over a semi-trusted third party.
Very simple POC implemented as part of the Israeli Mastercoin hackathon by Shaul Kfir (from Bits Of Gold) and Nadav Ivgi (from Bitrated).
Not suitable for production use, at all! Very messy, still missing networking and some security properties, and implements an older payment channel scheme.
A paper explaining how this works will probably be released in the future.
* The trusted third party basically acts as a centralized replacement for (the now defunct) nSequence. He cannot steal funds or collude with the other party to steal funds, but can publish older txs or delay publication (basically, get a free binary option).