Inter-destination media (play-out) synchronization for social TV has gained attention from research and industry in recent years. Applications include social TV and interactive game shows. To motivate further research of inter-destination synchronization technologies, pilot measurements of play-out differences in different TV-broadcasting systems are desirable. However to our knowledge no broadly applicable measurement system exists. This paper fills this gap by presenting and implementing a robust system that can detect constant or slowly varying differences in media play-out between different receivers without accessing receiver hardware or network. The measurements are relevant in various use-cases such as football watching, social TV, interactive game shows around TV-content, TV input lag comparison for gaming and validation of current inter-destination synchronization technologies. The robustness of the system is demonstrated in a working prototype.