Which Mac models will support continuity and Handoff on OS X 10.10 (Yosemite)?
System Requirements

Handoff and Instant Hotspot

Handoff and Instant Hotspot are supported by the following Mac models, and require OS X Yosemite:


MacBook Air (Mid 2012 and later)
MacBook Pro (Mid 2012 and later)
iMac (Late 2012 and later)
Mac mini (Late 2012 and later)
Mac Pro (Late 2013)


Handoff is supported by the following iOS devices and requires iOS 8. Instant Hotspot requires one of these iPhone or iPad devices with cellular connectivity and iOS 8.1. Instant Hotspot also requires Personal Hotspot service through your carrier.


Phone 5 or later     
iPhone 4s (sharing iPhone calls only)
iPad (4th generation), iPad Air, iPad Air 2
iPad mini, iPad mini with Retina display, iPad mini 3   
iPod touch (5th generation)


Phone calling

Phone calling requires an iPhone with iOS 8 and an activated carrier plan.
Phone calling works with any iOS device that supports iOS 8 and any Mac that supports Yosemite.

SMS

SMS requires an iPhone with iOS 8.1 and an activated carrier plan.
SMS works with any iOS device with iOS 8.1, and any Mac that supports Yosemite.

http://support.apple.com/kb/HT6337