I've been in Johannesburg for nearly 5 months now, and that crime is a huge problem in Jo'burg - and SA as a whole - is so well known that it's become common sense. Driving on SA's roads for 5 months has shown me a gaping hole in the GPS devices available here - the inability to specify "safest path" as an option.
Being new to Jo'burg, I really don't know which areas are (relatively) safe, and which are not. It has happened sometimes that I wandered-off into an area which I didn't know, and I didn't know whether it was OK to drive through that area (from a safety perspective). My GPS allows me to choose between "Fastest Time" and "Shortest Distance", but it doesn't allow me to choose "Safest Route".
I believe - with reasonable amount of confidence - that there's opportunity for a GPS device (or a feature in an online mapping service such as Google Maps) that provides such an option. How would this feature work? Based on historical records of crime-incidents and their respective locations, a "Threat Score" would be assigned to each area and recorded in the maps. The GPS would then not route the user through areas with a high Threat Score (or alternatively, a low Safety Score). For online services such as Google Maps, the maps could be live-fed with crime information as it happens, allowing the service to modify routes on a daily/hourly/whatever basis.
Such a device/feature seems to have opportunity not only in South Africa and the broader crime-ridden continent of Africa, but everywhere on the planet where crime is an issue.