yeah, i'm not sure the 9mm is a fisheye, I think the fov is somewhat less than 180, but I've seen many great images from it. The 15mm, not so many, not sure, but I think my phones would take as good or better images.
One option for you, is an slr lens on an adapter for 28mm. I have a 28mm/2.8 Konica, not sure if it's weatherproof, but a great 28mm, if the size is ok with you, and the IQ is pretty good, and usable in low light.
The 25/1.4 I have is pretty low quality, every image vignettes, soft edges, but it has a lot of character, like that 9mm bcl.