I am looking for an order management system that delivers VWAP or TWAP execution on various exchanges (including Polo and Bittrex).  Is anyone aware of any such system?  Please note, this is for VWAP/TWAP TRADE EXECUTION, not data analysis.  Haas, Gunbot, Leonardo, etc seem to only offer VWAP analysis, not execution.  The only one I can find that seems to offer execution is SFOX, and only TWAP for Bitcoin.   

Thx