One would usually look for stuff in stores other than Google Play, like Malavida App Store, either because you are looking for higher quality app selection and reviews or because what you are looking for is not available in the official Android store, such as WhatsApp MODs, modified versions of games, apps for downloading YouTube videos, games that are a bit risqué or applications that don't comply with Google rules.
Kali Linux in Android version
And that also goes for apps like those to be found in NetHunter App Store, a repository or catalog of all kinds of tools for auditing WiFi networks, testing penetration, analyzing vulnerabilities, spoofing or sniffing, protecting privacy, gathering information and a wide range of uses that in themselves are not an issue except for the fact that they can be used for unethical or dishonest purposes.
The app is developed and maintained by the same developers behind Kali Linux, distribution is aimed at data security, which is why it is no surprise to find many features similar to the those that we can use in this Debian distro. All of the apps are perfectly sorted by category according to what they are for and are regularly updated so that we can use the latest version.