Handoff feature devices requirement Why are supported devices for Handoff feature so strict to a small set of devices?

http://support.apple.com/en-us/HT6555
Handoff requires three things:


specific bluetooth hardware - this eliminates most of the older devices
specific wireless hardware - this has to do with MIMO antennas and a sophisticated wireless chip. This doesn't eliminate many devices as bluetooth capabilities were upgraded at the same time as wifi as far as I can tell.
a fast enough CPU


Thus the list of devices that support handoff is related directly to new hardware capabilities.