*reads said article* Damn, every time I thought I knew everything I needed to know about pee, someone comes along and astounds me.
Anywise, the article's got the general gist of it right (although you've gotta wade through a lot of historical and cultural stuff about our pee-drinking forefathers to get to it). Urine is reasonably sterile provided that the pee-provider keeps their southerly regions clean and doesn't have any urinary tract infections, and is perfectly safe in small amounts.
On the practical side (the article didn't go into that, although I'm sure the watersports article they've linked to does), your best bet is to have whoever plans on doing the pissing to drink a lot of water beforehand. Or better yet, low-alcohol beer. Or better still, full strength beer... well, except you probably don't want people getting drunk right before participating in kinky bondage stuff, especially in a bathroom with floors that are about to get wet and slippery. Anywise, all that extra fluid will not only help them pee, but it means it'll be a fairly diluted pee with a weak flavour (which could be a good thing if you turn out not to be as keen on golden showers as you thought you were).
As for poop, that stuff (obviously) isn't sterile at ALL. You run a serious risk of food poisoning, and any cuts or grazes you've got that come into contact might end up with nasty infections as well. So even if you've got a perfectly healthy partner, you're probably best to make sure that scat is for external use only. Eating it might make you spectacularly ill for the rest of the night, but I doubt your health is gonna be in grave danger just from making a mess of yourself.
rallan