Depends on what you term fisheye. By fisheye, I'm assuming your wanting to avoid distortion, in which case it's not just the lenses focal length or whether it's a "fisheye", but whether it's rectilinear that matters.
eg. Here's a 280 degree fisheye lens (admittedly at $3.5K a very expensive board lens), but just look how straight the lines are when fitted to a gopro (the video is 360 - just pull the pic to rotate):
So personally I'd find out what focal length is going to suit your needs (maybe using the CCTV view calculator), then start searching for a lens with the correct screw thread that's also rectilinear (and preferably viewing some video example clips shot on it to ensure it's truly distortion free).
Also, be aware the wider you go, the less pixels per inch you have and so the lower the quality / recognition, not an issue if you have another camera capturing a zoomed in picture, but maybe an issue if the ultra wide lens is your only lens.