Well, I've looked a bit into how the page handles those shiny things and came up with a script that should show an alert when a shiny pokemon is found. But I can't figure out how to get it working in this hackish greasemonkey piece of shit, I can't get it to replace the state_change_navi function with my modified one. But you get the idea. (this script works as a UserJS in Opera btw)
Of course I can't say this will work 100% because I haven't come across a shiny pokemon, but if you take a look at the state_Change_navi() function in navi_php.js
you'll see what I was aiming at in there.