The first thing that comes to mind when you think about proximity sensors is closeness. Typical sensing ranges of inductive analog output sensors include 2 mm … 5 mm, 3 mm … 8 mm, and 15 mm … 40 mm. So it’s easy to think that the target you want to detect needs to be very close to the sensor—within the physical limits of the sensing ranges. And you would be correct.That said, you can still use an inductive proximity sensor to monitor a process that is farther away, well out of the official sensing range. Using this method, the target acts as a proxy to detect something beyond the target itself. For example, if you set up the sensor to detect a target every time a cardboard box passes by a certain location on a conveyor belt, you can detect the number of boxes reaching that location—even when the boxes themselves are several feet or more away from the sensor.
To accomplish this task, you can mount the proximity sensor near a wheel that has different types of nubs. Each nub on the wheel can be distinguishable, for example by type of material, so that the sensor either detects the nub or not. Every time a nub made of metal moves within range of the sensor, the sensor recognizes the nub as the target, whereas a nub made of rubber goes undetected. The detection of the nub indicates the presence of an object, such as a cardboard box, farther down the line. This method can save you the cost of a more expensive sensor requiring a longer sensing distance.
As for practical results, every time a cardboard box is detected at a certain place on a conveyor belt, you can count the box, fill the box with product, have a label placed on it, scan the box to verify that a label has been previously placed on it, etc.
As far as what other sorts of applications work well with inductive proximity sensors, your only limit is your imagination.