XKI is described as 'Enterprise-Ready IoT Platform' and is an app in the Bitcoin & Cryptocurrency category. There are four alternatives to XKI for a variety of platforms, including Online / Web-based, Linux, Android, Chrome OS and iPad. The best alternative is Android Things, which is free. Other great apps like XKI are Xively (Paid), thethings.iO (Freemium) and Kaa (Freemium).
thethings.iO makes a real-time IoT cloud solution that supports REST, MQTT, CoAP and Websockets. It has a free account up to 3 devices, and then charges 1 Euro per thing per year for realtime storage, analytics, and interoperability features.