iPad navigation for South Africa
I'm not aware of any iPad specific apps for South African turn-by-turn navigation.

But, ALK Technologies, Ltd has iPad software for North America and Europe, and iPhone apps for South Africa - so I think your best bet would be to write to them or facebook them and ask when the South African version is coming out. If you're on safari and fleeing from lions and elephants I don't know if the iPhone version will be big enough to see clearly! 

NB: Apple.StackExchange.Com takes no responsibility for Lion or Elephant related accidents.