Tok is described as 'is easy-to-use software that adopts peer-to-peer communication, end-to-end encryption technologies. With Tok,you can send messages, photos, videos and files of any type without anyone else listening in' and is an app in the Social & Communications category. There are more than 10 alternatives to Tok for a variety of platforms, including Linux, Android, Mac, Windows and BSD. The best alternative is Tox, which is both free and Open Source. Other great apps like Tok are qTox (Free, Open Source), Antox (Free, Open Source), Toxygen (Free, Open Source) and uTox (Free, Open Source).
It uses the Tox protocol which is Peer to Peer, it will have a higher battery usage than other Messenger apps. If you are stuck with Antox or uTox (µTox) for Android, try this Tox Client that was especially optimized for Android.