There was a software equalizer out there I saw a couple years ago. I think it was made by the now gone elemental audio. Whatever it was, it had a notch filter that would filter in octaves. I've been trying to find another eq with that feature, but there seem to be extremely few if any and no easy way to search for it.
Assuming we're thinking about the same thing, it's not octaves, it's harmonics. The difference being that harmonics are doubles of the original harmonic, meaning for example the first overtone of 250Hz being 500, the secon one being 750 and so on. They are pretty hard to come by because they are mainly used to remove hum and such, though it can indeed be good for a lot of things. And like all filters, they are not EQ, just really really selective filters. Waves X-Hum is a good plug for things like this! Though it's a wee bit limited as it only goes up to about 3KHz as I recall.
Regretfully, really good notch-filters are pretty hard to come by, period. With an as steep slope as what they need, they can do pretty horrible things to the sound, as extreme Q can introduce quite a bit of phase-distortion. One plug I do use a lot to do this, however, is the good 'ol Waves Q10, with the bands set to 100 Q and finding each and every peak rather than relying on everything being perfectly spaced.
Izotope Rx4 hum removal. Lots of other great audio repair modules besides that as well.