best sensor for detecting object and approaching them

Using Arduino Sensors
#1

this sensor will be used on a robot arm

#2

Minimal information will get minimal response.

Weedpharma

#3

Btw, is it possible to have such sensor and detect eventual nearby animals in wilderness?

#4

Yes, of course.

#5

I should've said that the sensor would be on a wearable device.
If the sensor is on a watch, can it detect other moving animals/humans?

#6

What principal of detection do you have in mind. I am not aware of a sensor that is not at a fixed point that can detect humans of animals.

Weedpharma

#7

a PIR sensor, perhaps?

#8

A PIR is basically directional (I know they have lenses and can cover an angle). You would need a few around you and moving around would probably effect their operation.

Weedpharma

#9