It is real technology, although I don't think anyone is using it yet.
https://en.wikipedia.org/wiki/Pulsar-based_navigation

Using pulsars as a practical means of terrestrial navigation seems very unlikely

(My bold), you're right, I should probably have qualified this with "...in the near future".

External Quote:

X-ray pulsar-based navigation and timing (XNAV) or simply pulsar navigation is a navigation technique whereby the periodic X-ray signals emitted from pulsars are used to determine the location of a vehicle, such as a spacecraft in deep space.
... ...
In principle, pulsars are brighter in radio band, and have better-measured pulse profiles in radio, enabling up to meter-scale precision in navigation. However this would require radio antennas on the order of 10x-100x larger/heavier than used on spacecraft of the early 21st century. In contrast, X-ray receivers are much smaller (as their wavelength is shorter) and better suited for spacecraft.

Wikipedia https://en.wikipedia.org/wiki/Pulsar-based_navigation. The Wikipedia article mainly discusses X-ray based pulsar navigation in the context of spacecraft navigation.

This is because X-rays from space can't be consistently detected at the Earth's surface (if at all), or even at the altitudes most jets fly at.

External Quote:

...the inability of x-rays to travel long distances through Earth's atmosphere is startling. In fact, x-rays travel through the atmosphere over relatively short distances, less than ten kilometers, with the lower-energy x-rays being absorbed by air before the higher-energy x-rays. The atmosphere absorbs the x-rays of out space before they can reach any point on Earth's surface; in fact, short of going to space, the only craft that can reach an altitude high enough to observe cosmic x-rays is the high-altitude balloon. ... Today balloons are primarily used to test new x-ray detector designs. Almost all x-ray telescopes are now mounted on satellites.

Detecting X-rays, The Astrophysics Spectator 2.22 https://astrophysicsspectator.org/topics/observation/DetectingXRays.html

External Quote:

An X-ray telescope (XRT) is a telescope that is designed to observe remote objects in the X-ray spectrum. X-rays are absorbed by the Earth's atmosphere, so instruments to detect X-rays must be taken to high altitude by balloons, sounding rockets, and satellites.

Wikipedia https://en.wikipedia.org/wiki/X-ray_telescope

The Wikipedia article "Pulsar-based navigation" mentions one study investigating the use of pulsars for aircraft navigation,

External Quote:

In 2014, a feasibility study was carried out by the National Aerospace Laboratory of Amsterdam, for use of pulsars in place of GPS in navigation.

The reference/ link Wikipedia gives for this is is "Pulsar navigation: piloting aircraft with the aid of the stars", Extreme Tech website, 08 June 2015, Bauke Stelma. That article links to the actual study,
"PulsarPlane: a feasibility study for millisecond radio pulsar navigation", 2014, Buist, Hesselink, Gibbs et al., Proceedings of the 65th International Astronautical Congress (IAC2014) https://research.utwente.nl/en/publ...lity-study-for-millisecond-radio-pulsar-navi/

The proposal uses pulsar radio signals, not X-rays, so it could theoretically work for terrestrial navigation. But then the known current problems with pulsar radio detection come into play: Antenna size and detection/ signal integration time (often hours with smaller antennae).
The PulsarPlane authors have undertaken a theoretical study anticipating technologies that do not exist yet (but might do in the future),
from the paper,

External Quote:

Radio pulsar navigation - utilizing signals which could be detected on Earth - has not received much attention, since the signal strength of radio pulsars was deemed too weak to be useful. Advances in signal processing, analog/RF circuit design as well as antenna design, however, could enable faster and more accurate detection of pulsar signals, using a smaller antenna size. ...The study is part of the research project PulsarPlane under the European 7th Framework Programme as a pioneering idea, i.e. technologies and concepts that have the potential to bring step changes in the second half of this century and beyond.

(my emphasis).

A less optimistic European Space Agency study (albeit from 2004, processing times will have improved massively*) was based on existing technology (this was for spacecraft, not aircraft/ terrestrial use), summarised in
"Pulsar Navigation: a novel concept of spacecraft navigation?" European Space Agency Advanced Concepts Team https://www.esa.int/gsp/ACT/projects/pulsar-navigation/:

External Quote:

The study treated convincingly the characterization of suitable astrophysical sources and derived from this the minimal hardware requirements for a positioning system. This was done for both, radio and x-ray signals. The results are however not clear cut: a positioning accuracy of 1,000 km is attainable with a moderate antenna size (10 m2​) and a signal integration time of the order of an hour. However simultaneous observation of several pulsars with separate antennas seems desirable for a reduced integration time or an enhanced accuracy. This seems to require prohibitively heavy hardware.

Our technology is much improved from 2004, but the modelling then indicated that a platform with a 10 m2 ​antenna, in space (where pulsars are much easier to detect) could establish its position to within 1,000 km after an hour of signal integration.
This wouldn't be practical for terrestrial navigation, even if we allowed terrestrial antennae to be as efficient at detecting pulsars as spaceborne antennae.

The actual study is "Feasibility Study for a Spacecraft Navigation System relying on Pulsar Timing Information, Final Report", Sala, Urruela et al., 2004, ARIADNA Study 03/4202 https://www.esa.int/gsp/ACT/doc/ARI/ARI Study Report/ACT-RPT-MAD-ARI-03-4202-Pulsar Navigation-UPC.pdf

*I'm not sure if this has a proportionate effect on reducing integration times- the time needed to differentiate the weak pulsar signal from noise- which appear to be in part dependent on antenna size.