Measuring Latency end to end

Wowza Streaming Engine
1

We have a low latency video architecture working through Wowza that is performing really well - I think our average latency is about 2 seconds end to end. we take the video from a device to Wowza and publish the video over WebRTC using H264. The issue we have is that although our customer is satisfied with the latency they want us to report the exact end-to-end latency on the UI. Have you had other customers who have had this requirement? If so how did they solve this issue? Are do you have any ideas?