Liquid Feedback is the platform that catapulted the Piratenpartei into the state parliament of Berlin and has her at 7-10% in recent national polls. It's a solid implementation of the Schulze method combined with proxy voting also known as liquid democracy. Open source of course. Concerning the validity we use physical identification with testimonies and organize that in form of an association or political party. See http://piratenpad.de/occuliquid for more.