Threema lets you make end-to-end encrypted voice calls, send texts and voice messages. Share videos, and even conduct polls. Messages are deleted after delivery, and local files from conversations are encrypted. Several other features are in place to protect your privacy, too. The app is 2-99 for iOS and Android.
Telegram Messenger app connects you via a unique distributed network of worldwide data centers. A syncing feature lets you send and access messages from all your devices at once. You can start a conversation on your phone and finish it on your tablet or computer. Create group chats for up to 200-thousand members. Share large videos and documents, and even set up bots for specific tasks. The app is free for iOS and Android.
Signal offers advanced privacy and is used by millions every day sending and receiving messages. You can make HD voice and video calls. The app secures your conversations end-to-end. As a bonus, you can use your existing phone number and address book to securely communicate. There are plenty of other great features, too. The app is free for iOS and Android.