WEFOUNDLilongwe, Malawi - GPS Navigator

Hi sat nav is not really needed in Malawi, as the road network is pretty simple, and a few directions is all you need, but I would guess that one would be useful in the other countries you referred too. There is a guide called Track4Africa that I have seen recommended, although I have no personal knowledge http://tracks4africa.co.za/

I'm planning on taking an iPhone and a Garmin 450. We won't be driving ourselves, so I don't think I'll need GPS, but am just taking them to play with. Probably the most use I see is if we want to walk to/from our hotel in Blantyre to the city center.

to generate Garmin-compatible maps from OpenStreetMap data. For the iPhone, I'm using a free version of MapsWithMeLite which uses maps from OpenStreetMap but also allows you to pre-download them so that you have maps access even without a cell or Internet connection.