That's right - I made polenta in my rice cooker. And it was fantastic.
I used to complain about this rice cooker because I felt like it was really slow, taking nearly 40 minutes for a batch of rice, whereas I only needed 20 minutes to make it on the stove. (My mom said that was the sign of a really good rice cooker, but I think she was just trying to make me feel better.) Certainly I can make polenta on the stovetop, as I can with rice, but you have to pay attention more (and I burned the last couple of batches of rice that I've made on the stove, which, as an Asian, is kind of embarrassing). So I like this method because it's totally hands-off and I can do other things while it's cooking.