In the movie Unfriended: Dark Web, hacking drives many of the events. The Circle hacks the group's computers, phones, and cameras, amongst other things. At its root, hacking relies on vulnerabilities that lie within these technologies, which are then exploited by a malicious actor.
An article written in 2018, the same year as Unfriended: Dark Web was released, outlines the vulnerabilities that exist in apps and programs that use smart phones' geolocation data. The vulnerabilities were discovered by two security researchers Vangelis Stykas and Michael Gruhn, who found that "easy-to-guess passwords (such as 123456), exposed folders, insecure API endpoints, and insecure direct object reference (IDOR) issues" can enable third parties to gain access to personal information and GPS coordinates of location enabled devices [1].
In Unfriended: Dark Web, Charon 4 tracks Amaya by hacking her phone- presumably exploiting a vulnerability within the location services of the phone.