Blood speed isn't a particularly useful metric. We're typically more interested in the volume of blood circulated, as that is a better measurement of blood (and therefore oxygen) delivered to end-organs. Most organs are very good at regulating the speed of flow through their supply, and are more dependent on volume of flow.

One of the more useful measurements we look at is cardiac output (CO). It's just the stroke volume (how many ml of blood is squirted out of the heart every heartbeat) multiplied by the heart rate. This tells you how many ml of blood are sent into circulation every minute. Doppler imaging can be used to show flow speed, though that's much less useful. Measuring CO is relatively easy to measure and is a useful measurement of how much blood is being made available to end organs. The heart rate is very easy to count or calculate, but the stroke volume does require an ultrasound study (preferably a transesophageal study). For an even more useful measurement, you can divide that CO by the person's total body surface area to get the cardiac index (CI) this gives you a more standardized number from person to person, which allows a more meaningful comparison than CO alone.