I've heard of the ping-pong ball method, been meaning to try that....if you do, let me know how it works out! :D
Another thing you can do is put things around the tank, like action figures, a picture....something for them to look at. I only have two bettas who are alone in their own tank(for now), Sasuke and Smore. Sasuke lives next to my computer(where I spend a good portion of my time)so he always gets to watch me. Smore is on my dresser and I always set decorations and all sorts of things up there for him to investigate. Like now I have a small fake Christmas tree right next to his tank, and hes rather fascinated by it.
Usually in a divided tank, the bettas will eventually become used to one another after a little while and you want to put plants up to break up the line of site, but they also keep one another entertained with occasional flaring and things of that nature. At least, mine do
A 1/2 gallon is too small for anything to live in long-term. Its fine for temp. housing for a betta if you have NOTHING else, but otherwise they're pretty useless.....