I'm still fairly new with Mac's, but I have been using a USB 4.0 dongle for using knock to unlock my mac with my iPhone on a 2008 Macbook pro. It worked great under Mavericks and I never had any issues, but with Yosemite, I have noticed that the BT 4.0 device will connect and disconnect over and over, which essentially makes knock unusable. Can anyone help me out with this??