http://www.macrumors.com/2014/10/23/...tivation-tool/

With iOS 8 and OS X Yosemite, Apple introduced "Continuity," a set of features designed to allow for deeper integration between Macs and iOS devices. Unfortunately, some Continuity features are limited to Macs with Bluetooth 4.0, which leaves many older Macs unable to access the new features.

Additionally, even though the 2011 MacBook Air and 2011 Mac mini include Bluetooth 4.0, Apple has opted not to allow them to access Continuity features. Luckily, many resourceful members of the MacRumors forums have come up with solutions to allow them to enable Continuity on their older Macs, and discussion on our forums has led to the creation of a set of instructions and a Continuity Activation Tool that should get Continuity working on Macs unable to explicitly support the feature.