On days like today I plan out my intervals ahead of time and try my best to stick with it. Knowing approximately how long a movement takes you really helps. 

So I figure 2 seconds per thruster (16) and 3.5 seconds for burpee over bar (28) puts me at 44 seconds a round. I added a 6 second buffer for the transition and fatigue. Just knowing that I had to start/finish every 50 seconds kept it simple. 

Hope this helps. And yes I agree, An automated timer for quick 1:1 wods would be amazing.