Was out in the garden this morning and looks like both of these are ready for action. This cross is highly unlikely to work but that just makes it even more fun to try - I'm going to use Vigna unguiculata (cowpea / black eyed pea) as the pod parent and use Vigna radiata (mung bean) as the pollen parent. There are quite a few visible differences in appearance that could show up in the offspring (if I even get any). In the first picture, the cowpea flower is the huge pinkish one; mung bean is the yellow smaller one. All parts of the cowpea are smooth and hairless including the pods (behind the flower); mung bean pod (at bottom) is furry. In the second picture you can see the contrast in size color and furriness of the cowpea foliage underneath the mung bean foliage.
So, if I get any seedlings showing olive green foliage, hairiness or yellow flowers it would be really cool. When they finally decide to quite growing so much and flower, maybe I should try using some of my F1 hybrid cowpea seedlings from last years crosses ('Black-Eyed' X 'Tetapeche Grey Mottled')as pod parents (with mung bean pollen). I've read that hybrids are often more willing to accept wide crosses.
Oh I almost forgot... mung bean has olive green seed coats. I don't think any cowpea varieties have this color. So that's another trait I'd like to see show up in offspring using cowpea as pod parent.