So from reading the CBPeripheralDelegate documentation, it appears that RSSI and peripheralDidUpdateRSSI:error: were deprecated with i
In iOS 8.1.1, peripheral:didReadRSSI:error: will only get called for peripherals that you are connected to. If you've merely discovered the peripherals with a scan and then called readRSSI on them, the callback will not be called.
Try connecting to the peripheral first (via CBCentralManager's connectPeripheral:options:), and then calling readRSSI.