The raw computing power you have in your pocket right now would have filled entire buildings just a few decades ago. Think about that for a moment. And like Spider-Man can tell us, with great power, comes great responsibility. How are you keeping your phone safe? How are you protecting your data, and avoiding malicious apps? If yon don't have good answers to those questions, you need to follow these channels.
PRISM Break by Pranav Ganapathiraju takes government surveillance to heart, as should you. Pranav offers several alternatives to cloud-based products, and tries to find apps that would let you keep the functionality you enjoy while doing a better job protecting your privacy. For example, he suggest you use Orbot to surf the Web via the Tor network, helping preserve your anonymity. Another suggestion is Surespot Encrypted Messenger, to "take back messaging."
Don't let the name scare you away – Hacking is not always used for evil. Hacking by Igor Miladinovic includes tools like Cryptonite, an open-source encryption solution based on EncFS (or, in other words, a way to keep your private files secret). You will also find RedPhone, a tool that claims it offers end-to-end encryption for phone calls.
Much like PRISM Break, Hacking doesn't contain only security apps. It's a broad channel, so you'll find gems like classic code editor DroidEdit. After all, "hacking" means programming, too.
Root & Security Apps by bagiueli has just twelve apps, and yet it has amassed over 570 followers. That's an impressive achievement, which might have something to do with the careful selection of apps. The channel offers AVG's Mobile AntiVirus Security PRO, an $11 product – I didn't even know AVG offers a commercial anti-virus, and I was using their free one for months now. You will also find Cerberus anti theft, which is a powerful anti-theft solution with a good business model: You pay just one time, rather than a monthly fee.
Like I wrote at the beginning, security and privacy are serious topics. Don't believe every word an app tells you – try to install open-source, peer-reviewed privacy apps, rather than just commercial apps which may or may not have backdoors and security holes. Stay safe!