This seems similar to bounceexchange[0], and I think the idea is generally good. Try to grab people's attention at the last minute when they're already planning on leaving your website anyway. Last-ditch effort that can't really upset too much, especially since you already lost them. Of course it depends on how spammy those popups end-up being, but at least from a couple of sites that I've seen and who use bounce exc…
I've come by quite a few websites recently who fire this in my face prematurely. It feels rather annoying to get a "please don't leave us" pop-over when all I wanted was to move the mouse out of the way so that I could read the site's content (which is now impossible due to the aforementioned pop-over).