The honeypea is a cowpea which is a bean. A large variety of useful types, bush and vine, make it a popular legume in warm climates. Black-eyed peas are cowpeas. It took me a while to work all that out.
I have looked around the web and find beekeepers think it makes a good light honey. Not all beans are cowpeas, though, so you can't assume a field of beans will attract bees.
The bloom of the cowpea is of such formation that the proboscis of the hive-bee is too short to reach down to the nectaries; but just beneath the bloom are a number of little glands that secrete a sweet substance that is largely sought after by the bees. I have seen them work on it from morning to night.
In 1920 Frank Chapman uses testimonials in his American Honey Plants: Together with Those which are of Special Value to the Beekeeper as Sources of Pollen:
The cowpea is widely cultivated in the warmer regions of the old world and in our own Southern States. It is grown for forage and for green manure. The plant is more closely related to the beans than to the peas.
R. A. Nestor reports that it yields freely in east Texas, and where planted in sufficient acreage yields surplus. The honey is very dark in color, but of mild flavor, according to his report.
The nectar from cowpeas is secreted by extra floral nectaries and beekeepers are often mystified because the bees are working at the "joints" instead of on the flowers. Some report that bees gather nectar from the flowers, also.
The following reports indicate the value in different localities:
"There is no finer honey plant than the cowpea, while it lasts, but it blooms only about a week. During this time, if the weather is fair, the bees swarm over the fields from early morn till dewey eve."—J.D. Rowan, Tupelo, Miss. Gleanings, Sept. 15, 1909.
"The cowpea is one of our most abundant sources of honey for late summer. The crop is planted here from May 1 to August 1, and furnishes nectar through a considerable period of otherwise scarcity. Unlike other plants, the stems, and not the blossoms, secrete the nectar as the young pods are forming. These the bees work upon excessively. The honey is of good body, thick, deep, approaching dark yellow in color, and of strong taste like that of tulip-poplar, only stronger, with a somewhat slight, wild-green-bean-like flavor."—C. C. Gettys, Hollis, N. C. Gleanings, Sept. 14, 1909.
"A small patch of peas was covered with bees from morning till night. Nearly all of them were working on the stalks, as usual; but here and there I saw a few Italians pushing their tongues down into the blossoms. I have never noticed any pollen from the field peas."— Mrs. Ameda Ellis, Fremont, Mo. Gleanings, June 1, 1910.
Below a bumble is nectaring on those floral nectaries at make the cowpea family useful to beekeepers.
"The peas bloom when there is a honey dearth and the bees gather honey from them. However, I notice they do not work on them much if there is a better honey plant blooming at the same time. My bees get a good deal of nice honey from them."—G. H. Latham, Jr., Rapidan, Va. Gleanings, May 15, 1910.