Blueberry shrubs are a possibility. They prefer acidic soil
just like azaleas. They also like plenty of sunlight.

How about black currents? Would they make a good substitute for azaleas?

Black currant berries will leave stain on siding if planted close to house and eaten by birds. Plant red ones or gooseberries. Red currants are a little bit easier to handle and they can tolerate more sun than black.

If you have enough sun for blueberries, take a look at the link below for details of growth habit and coloration (as well as fruit details) for many blueberry varieties. You can match the blueberry habit to that of your azaleas, if you're happy with the visual function they serve in your landscape. BTW, this nursery also gives info on half-high cultivars, and they are the ones which will match the lower spreading azaleas. You may not be able to order from this nursery, but it's the best site I've found for detailed descriptions.

Here is a link that might be useful: blueberry lists

Blueberries are a great choice but remember that they are not evergreen. They can be quite attractive in the winter without leaves however if you choose those that have red twigs.

If you have room for ground cover plants, I would recommend lingonberries and alpine strawberries, both yellow and red. Both plants are attractive for many months of the year. If you are worried about fruit stains, perhaps white currents or gooseberries would work for you. You may be able to grow a dwarf quince or a paw paw as well which are taller than blueberries.

Cheers!

Don't count on lingonberries working for you in those hot, humid summers- they tend to get fungus in those conditions. Sunshine Blue is an evergreen (at least semi-evergreen) half-high blueberry variety- good choice! Also consider putting up a short run of split rail fence and letting a grape or two grow on it.