If you have limited space you can plant them in the same hill.

Use a whole potato. Scoop a hole in the potato the size of the tomato plant's root ball. Set the tomato into the hole and plant the entire thing in a hill.

Make sure to water and keep well-nourished. You will get potatos in the ground and tomatos on the top.

Then you don't have to find a use for the potato fruits.

They're quite toxic. I guess in theory you can turn them into a spray for whiteflies and aphids, similar to they way you might make a garlic spray, but I don't know the details.

But the seeds definitely can be saved to start a new generation of potatoes in your next growing season. Not very hard, treat them just like you would a tomato, eggplant, or pepper, same growing conditions. Give them about a 6 to 8 week headstart before transplanting to the field.

I have many potatoes as they volunteer in the compost piles. I might have been tempted to try those.

Funny you mention it though, because my husband was just saying that if this year's crop sprouted some we might try growing potatoes from seed next year. At least trying a few. If you give it a try let me know and I will do the same, provided we actually get some fruits this year. So far none have been spotted.