Can a baby Doppler be used to measure blood pressure in animals, or adult humans?

Not sure what you mean. You measure blood pressure with a blood pressure cuff and a stethoscope. You could use a doppler instead of the stethoscope to determine when the pulse is cut off, but not a "baby doppler".

The baby doppler does not measure blood pressure. It detects movement. When the probe is directed towards the heart, the movement of heart is detected using doppler principle. That is heard by audible sound. It also counts the number movements showing as pulse rate.

Now coming to using that device on adults or animals. As long as you just need to know the movement and rate at short depth, why not.