i got one for my partly-blind HMPK, Theo, when i got his 2.5 gallon replacement tank(the 2.5 gallon KK i bought for him was cracked at the bottom. >.>). i was gonna use it, to train him to eat his pellets off it, since he wasn't able to see the pellets till they sunk to the bottom, then didn't recognize them as food till they sunk into the rocks. after getting it out, and looking at it, i noticed the wire inside it was visible! i took a pair of needle-nose pliers and ripped it out. now, it's just silly-looking. >.> all droopy. i'm thinking about "ghetto-rigging" it, so it sticks out straight and sturdy, with maybe some plastic and silicone.
Haha, I was thinking about making a thread about this, and lo and behold, there is already one!
I saw one at my local petsmart. I was thinking about buying it, but decided to hold off for a while. The reviews on petsmart.com for it seemed pretty good, but I can never trust those reviews! LOL.
Cravenne's idea of making one sounds pretty good, I'd recommended trying that, I am going to try it!
I have one in each of my 2.5 gallon tanks. I've never noticed any metal or anything. There hasn't been any rusting either, but I haven't had them long. One of my bettas likes to swim underneath and rest on top of his. The other completely ignores it. Like I said, I haven't had any problems with mine (yet), but whether or not a betta will like it depends entirely on the fish.
Theo doesn't give two licks about his. >.>; it'd help if he could see it, though. x3c he does like to rest on his one plant, though. it has wide flowers on it, so it does the same thing the hammock does, only better(betta. xD aahh, corny).