I used a cheap Garmin nuvi sat nav on my last Morocco trip - I found it really useful for giving your general bearing, and it even though it only has European mapping, it did contain quite a few main roads and even some of the primary pistes in Morocco.

In conjunction with a map it certainly saved me a lot of problems navigating routes. A useful feature on the Nuvi is it will give you your GPS co-ordinates (not sure if all other units do this?) - I was able to navigate across open harmada to known way points using this , so again it was extremely worthwhile.

The main problem I had was in navigating to a location I did not have a known set of co-ordinates for - it's all very well knowing your precise location on the planet, but if you can't translate that GPS ref onto a map it's fairly useless.

I will definately be investing in a proper GPS unit now though as I would have liked to have recorded some of my waypoints properly.

Not sure if my little sat nav unit would be any good on the trip you're planning though, but I've used Google maps with great success on my mobile phone, if only just to double check you are where you think you are...

I use a laptop for my maps when I travel.
The GPS is a Garmin Etrex (app £90) this tracks the satellites and gives me my position on the laptop, this enables me to see; where I am, and where I want to go. In UK and europe I use Microsoft Autoroute Express, and in Africa, Fugawi World Explorer, which has a world map, and I buy the Geo Ref'd maps from Darr as they have many areas of the world covered. Obviously the laptop has many other uses, and the Etrex can go with you when you leave the car to remind you where you parked it.
Kevin