USB Bluetooth 4.0 Adapter

echo 0a5c 21e8> /sys/bus/usb/drivers/btusb/new_id
hciconfig hci0 up

Confirm it works:

root@Arduino:~# hciconfig
hci0:   Type: BR/EDR  Bus: USB
        BD Address: 00:02:72:33:96:0A  ACL MTU: 1021:8  SCO MTU: 64:1
        UP RUNNING
        RX bytes:2145 acl:0 sco:0 events:84 errors:0
        TX bytes:187 acl:0 sco:0 commands:42 errors:0
hcitool lescan --duplicates 1>/dev/null &
root@Arduino:~# hcidump -a
HCI sniffer - Bluetooth packet analyzer ver 5.13
device: hci0 snap_len: 1500 filter: 0xffffffff
> HCI Event: LE Meta Event (0x3e) plen 39
    LE Advertising Report
      ADV_IND - Connectable undirected advertising (0)
      bdaddr D0:B7:E8:DE:F3:00 (Random)
      Complete local name: 'Rtrivr_R621'
      Unknown type 0x19 with 2 bytes data
      Flags: 0x06
      TX power level: 0
      Complete service classes: 0xf000
      RSSI: -68
> HCI Event: LE Meta Event (0x3e) plen 12
    LE Advertising Report
      SCAN_RSP - Scan Response (4)
      bdaddr D0:B7:E8:DE:F3:00 (Random)
      RSSI: -65

Move iBeacon further a part distance will reduce RSSI, -6dB seems to be double the distance.