The Relayr C# SDK by Relayr offers an Internet of things platform that can be integrated with existing applications. It features a cloud solution for receiving and saving data from sensors. It requires the M2MQTT and the Newtonsoft.Json references.
One of the bigger challenges with anything having to do with software-as-a-service (SaaS) applications is how quickly they can sprawl out of control. Before most organizations realize it they wind up with multiple silos of SaaS applications that are even more difficult to integrate than traditional enterprise applications.