I'm not going to pretend to know much about Ghanaian cuisine, or even enough about it to confidently say that this truly is a Ghanaian dish. The story of this recipe is that I was on temporary duty to Fort Belvoir and found a Ghanaian restaurant near where I was staying (Rahama, right off U.S. Route 1) and ordered their Waakye, which came with a seemingly tomato-based stew. It was probably the best take-out I've had in my life, so I did some research and landed on this recreation.
This is also quite spicy. I once offered a bowl to my partner and they were unable to finish more than a bite.
Within the last hours of cooking, hard-boil some eggs, peel them, and add them to the stew, along with the shrimp or crayfish powder. You want them to absorb some of the flavor from the gravy while not completely overcooking them.
Cubeb tail pepper and calabash nutmeg will probably be hard to find if you don't have a local African grocer. Before I moved to NoVA, I'd substitute regular black peppercorns for the cubeb tail pepper, and regular nutmeg for the calabash nutmeg. You can also skip the smoked shrimp/crayfish powder if you're having trouble finding that.
The nice thing about black-eyed peas is that they cook relatively quickly without soaking, so I just cook them straight from dry in this recipe.
This recipe probably could be done in a slow cooker or similar appliance, just ensure you get enough browning on the tomatoes during the initial frying stage.