From January 1st 2016 the use of an FIA homologated FHR is mandatory in MSA National events for the following in Sprints and Hillclimbs.
All drivers with the exception of road going category vehicles and period defined vehicles (pre – 1977)
A full list of FIA homologated FHR systems can be found at FIA technical list no 29.
The FIA technical lists can be found at http://www.fia.com/homologations
For more information see the document from the MSA: