Charles Proxy - HTTP proxy / HTTP monitor / Reverse Proxy
Firebase - Firebase is a cloud service designed to power real-time, collaborative applications for mobile and web.
Wireshark - Wireshark is a network protocol analyzer for Unix and Windows. It lets you capture and interactively browse the traffic running on a computer network.
restdb.io - restdb.io lets you create databases and REST APIs quickly. Development databases are free. Powerful web-based and mobile-friendly data management.
Postman - The Collaboration Platform for API Development
RemoteStorage - An open protocol for per-user storage OWN YOUR DATA