I use entropay.com, which lets you create virtual credit cards, and pre-charge them. And if the account runs out of money, the transaction is declined, and the merchant has no way to get your money after that.
As a warning, there are some problems with entropay.com though. Over the last year, some merchants have been able to detect that entropay.com virtual credit cards are prepaid, and require a plastic card. Also, entropy cards are from Malta, so companies like Spotify or Netflix will only give you access to content licensed there. Finally, and most importantly, entropay.com has a tendency to "float" your money, and I've heard that sometimes they just snatch it. I've never dealt with more than $150 at a time.
Since they are based in Malta, I think it would be very hard to dispute anything with them. But if you have to do any bigger transactions, you should use a bank here anyway. But it's great for trying out services where you don't trust them, or are just concerned with overages. I use them as a buffer for a lot of recurring payments.
I've seen some services on hackernews that offer virtual credit cards, but the problem is, that they all are tied to some underlying checking account, and even if the prepaid balance is declined, the company is obligated to somehow collect the money, if they can. There's no way to simply cancel a recurring payment. I'm sure that this is because they are required to by banks in the US.
I really wanted to have a complex money firewall, like you describe, but in practice, I've ended up just using plain old credit cards for most things. It is still very good to have an entropay account, though.