Just adding my echo to what Tonberry and Redpepper have said.
Personally, I have this same kink in a big way. But in my mind, polyamory only would start if this kink became something more serious between your wife and her/your kink partner. That's me talking only; there is considerable difference of opinion about what is polyamory and what isn't.
And it sure does sound like your
fantasy, not hers. Not fair to push her into it if so.
I really like RP's idea of finding a gf (sexual or non-sexual) to share this sort of voyeurism with. Also it would be a safer emotional venue to explore it with someone who wasn't as important to you as your wife. Any idea how she would react to this idea? If nothing else, talking about it might help her understand just how serious you are about wanting this.
Side note to Redpepper:
I would have no problem friending someone that likes to here my stories and perhaps watch me and my loves have sex because it turns them on. Dressing up for them, having them watch me at a bar at a distance. I would get off on that greatly.
That is so fucking hot. I would totally love to be on either side of that, as the voyeur or the exhibitionist.