Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Thunkable - Powerful but easy to use, drag-and-drop mobile app builder.
WhatsApp - WhatsApp Messenger: More than 1 billion people in over 180 countries use WhatsApp to stay in touch with friends and family, anytime and anywhere.
MIT App Inventor - App Inventor is a cloud-based tool, which means you can create apps for phones or tablets right in your web browser.
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.
Bubble.io - Building tech is slow and expensive. Bubble is the most powerful no-code platform for creating digital products.