Web Bluetooth - a web API under development, and will be one of the core components of Web of Things, the application layer of Internet of Things. It will enable sensors, beacons and user devices to communicate with each other. But at first: it will enable a web browser to contact the user's connected devices such as smartphones, kettles, toasters, TVs, thermostats, heart rate monitors, and so on. Imagine a world where every web site can connect to devices near you - or on you.
It's imperative to design this layer with security and privacy in mind. We currently experience some of the cheers related to widely distributed Internet of Things devices used as massive attack tools.