'Speedometers' we called them, that's about the only info they gave us, if they had cadence and heart rate they were huge! Before the days of GPS we had to fit a sensor to the spokes and measure our wheel circumference.
Now we have a colour led display that pics up everything from our phone and even bike fit sensors that advise us how aero we are, where other riders are on a virtual google earth or map segment, power, HR, cadence, crash alert, car proximity and even when to eat next.
Reliability, simplicity, after sales service and user friendliness are key variables. We want to know which worked best for you?