Microsoft's personal assistant Cortana is not officially available on OS X, but that hasn't halted Parallels releasing version 11 for the Mac, which not only includes full support for Windows 10, but also Cortana too.
With Parallels 11 installed and a copy of Windows 10 loaded, a simple "Hey, Cortana" will bring up the personal assistant. But what's more interesting (and a neat feature), is how you're able to activate Cortana even while using other Mac app. The assistant will appear on top of said windows and allow you to carry out searches.
Also included in Parallels 11 are performance improvements for booting up Windows and the whole experience should be a little lighter on your portable battery. Be sure to check the official blog post on the Parallels website for more details, as well as make a purchase.