I keep my viv in my home office and never let the cats in there. I never let them in there even before I got my beardie, because cats + important cables everywhere = a bad equation.
My kitten has taken to sleeping on it. I'm asleep then too so squirting him is out of the question...
I've considered putting an electric fence around it. Horses learn quick to stay away from them usually with just one shock. But then I run the risk of touching it myself. And honestly I don't want that humming thing inside.
I've not done it yet but my vet says double-sided tape will work to keep them off of things. You could try a couple strips of that and see how it works.
Instead of electric fence how about one of those invisible fences for dogs with the shock collar. Just set the sensors up around the Viv.... It could possibly work.
I usually shut my door, but the cool air conditioning from the main room doesn't get to my room, so I have to leave it open most of the time. My kitten likes to sleep and hang out on top of the viv, but Sol finds it really annoying. I have had to kick her out of my room so many times, I think she gets the hint. I might have to move to the water spraying method if she starts at it again. My other cats just stare at him from a distance for a few minutes then leave, so I don't have to worry about them too much.