Windows Store Apps
In Windows 8.1 the Windows.Devices.Bluetooth namespaces provide support for Rfcomm connections and Bluetooth Low Energy GATT services. As with Windows Phone there is no functionality to pair with devices - you can only connect to devices the user has manually
Inthehand.Devices.Bluetooth.Sdp provides some helper functionality to correctly format SDP attributes (and Records) which can be set using this API.
In Windows 10 the API is enhanced and is now universal across Phones, PCs and IoT devices. Rfcomm background tasks are possible on all platforms (previously phone only) and there is a DevicePicker control built-in.