ThingSpeak - Open source data platform for the Internet of Things. ThingSpeak Features
Firebase - Firebase is a cloud service designed to power real-time, collaborative applications for mobile and web.
The IoT Guru - the IoT cloud backend company
Supabase - An open source Firebase alternative
AskSensors - The easiest IoT platform
Etebase - Etebase makes it easy to build end-to-end encrypted applications by taking care of the encryption and its related challenges.