Yeah, that should be my title! Do you know that cat urine phosphoresces (glows) in the dark if viewed under a black light (Wood's Light/UV light)?
If you fear your cat is urinating somewhere in your house, but can't find it, simply wait 'til evening, turn off the lights and grab a black light. Simply by sweeping the area with the light, you'll suddenly notice dribbles on a wall, puddles on the floor, or odd stains on the furniture. If you're not positive it's urine and think it's some other stain, you could be right! You might have to take a sniff of the area to be sure. Don't get too close though! Yecch!
I've use this method many times before and it works well. It also, sadly, works if you got to a hotel and run the black light over the bedding! "Other" stains will appear..the kind you don't want to know about. You might want to leave the black light home!