That's not a fair comparison Steve.
You can tell when a cyclist jumps a red light in the exact same way as you can when a driver jumps a red light. Using your comparison, you can still tell if a car is speeding using the mobile phone if you film it and then compare landmarks: That's how the CPS do it, albeit they don't usually have to rely on mobile phones.
I can prove very easily that a driver is ignoring road signs telling them to stop or give way, not wearing a seat belt (easy to see at 30mph, try it!), on a mobile phone etc. It's just as simple to see the obvious things, no matter your mode of transport.