How does Bluetooth improve location accuracy? I noticed that iOS 7 on my iPad now says this in the Bluetooth pane of the preferences if Bluetooth is turned off: "Location accuracy and nearby services are improved when Bluetooth is turned on."

How does Bluetooth improve location accuracy? I know that Wifi improves accuracy because Apple has various Wifi networks mapped out, but how could Bluetooth help?
iOS 7 introduced support for Bluetooth Low Energy (BLE) iBeacons. These are small Bluetooth devices that can be placed to indicate a very specific location and the system respond in some way when they are detected. Enter a shop and an app for the shop showing you the latest offers might be one way for this to be leveraged. This would be different from usual geolocation APIs which become inaccurate when you are inside large structures (offices, malls etc.) as they cannot get a GPS fix, and WiFi coverage tends to be meshed with repeater stations