SharePoint 2013 OOTB lookup list filtering

Problem: 
I don't want to start customising my solution and I need a lookup column with restricted options.  I read this post from April Dunnam via Google and it's awesome and I wish I had thought of it first.

I have 2 lists: Countries (Country, Continent) & Business (Name, LocationInAsia, LocationInEurope).  I want to be able to specify their head office in each continent.  I could do a lookup list to country and show all the countries or I can use Aprils approach and only show Countries for the specific region.  This is a contrived example but it's a simple way to explain it.

Resolution:
On the Countries list create a Calculated column/field, call it "AsianCountries". 
The formula is =IF([Continent]="Asia",Country,"")
On the Business list, create a lookup called "LocationInAsia" that points to the "AsianCountries" field in the Countries list.

http://www.sharepointsiren.com/2013/05/sharepoint-2007-2010-2013-filtered.html

Summary:
This is pretty useful in that I don't need to write and custom code to have lookup lists that only show the appropriate content.  Sure I need to have extra calculate columns but a good no code way to restrict lists lookups.