Why would anyone need this? You have more chances of getting sucked into a black hole than successfully cracking a key with balance.
That's assuming the key isn't actually a brainwallet.
But the fundamental problem with tools like this is that people do not use BIP39 phrases of small word length unlike the short, predictable strings that you see as input to brainwallets. It's not like there's some unfortunate dude somewhere that's using 3 or 6 words for the seed phrase.
In fact, there's no such thing as a "BIP39 brainwallet": The vast majority of people use 12- or 24-word phrases, so iterating through all possible combinations of words becomes impractical. To me, this looks like a slower version of BTCrecover.