In the wild they will eat fruit including the seeds. In fact for a chipmunk, seeds are the best bit. Just don't give them the seeds from apricots and nectarines. I think I wrote something about apricot stones on this board, but just can't find it right now.
All these fruits I've tried over the years without a problem:
Pumpkin (they love these cut in half)
Grapes
Cherries
Apples
Pears
Oranges
Butternut Squash (they also love these cut in half)
Star fruits
Dragon fruit
All squashes
Kiwi
Blackberry
Red and black currents
Sunflowers
Peppers
I do also give them plumbs and avocados, but for those two, I don't give them stones.
Mate of mine has a bush with loads of rose hips on it, I think they maybe seeds or seed pods, can't you make tea with them. I think the local birds like them, but I don't want to experiment with rose hips on my chippies. The are like little red berries, and I will try and remember to take a photo next time I'm round there.
