Despite years of hearing about “easy wireless mesh,” developing practical wireless sensor networks that can be delivered and installed successfully at scale has remained a complex and elusive endeavor. Many practical IoT applications are not suited for simple cellular or WiFi connectivity due to energy and cost constraints, and most approaches don’t scale to hundreds- much less thousands of devices. This talk covers the technologies, tools, and tradeoffs involved in building successful, commercial wireless sensor networks at scale. We’ll discuss and demonstrate real-world examples of the software challenges inherent in IoT applications.