I've been working on application that receives health data trough BLE. It's been working correctly in background and sending the notification when in specific conditions. Problems, unfortunately, occured when I installed the iOS 8.1. It doesn't trigger peripheral:didUpdateValueForCharacteristic while in background. When I go with the app back to foreground - it receives data correctly.
In Info.plist -> UIBackgroundModes bluetooth-central is added.
My tests shown, that in 8.0 it was still working.