Why ECG app is not available in South Africa

Due to the medical reasons, Apple must receive regulatory approval before launching the electrocardiogram analysis in a country/region.

Nobody here knows if/when it will be available in South Africa.

As you probably already know, here's a page where Apple lists the features availability on country basis: https://www.apple.com/watchos/feature-availability/#apps-ecg

Generally it depends on your government's health agency giving Apple approval to us the ECG app in your country.

But since this is a user-to-user technical support forum, the volunteers here do not have any knowledge about talks between Apple and your government.