PlatformIO - Next-generation IDE for IoT
Losant - Losant makes building connected experiences and solutions easy.
B4R - Development tool for native Arduino programs.
Hologram.io - Cellular IoT connectivity that powers innovation
openHAB - "empowering the smart home" - vendor and technology agnostic open source home automation
Cisco Jasper - Jasper provides a SaaS IoT platform to enable companies of all sizes to launch, manage and monetize IoT services on a global scale.