This is an idea that’s been needed for a long time: Amazon will soon be adding the ability to make purchases of apps and games with a virtual currency known as “Coins,” according to this Amazon press release.

Here’s a question I see parents asking all the time: “How can I limit the purchases my children make on their new Kindle Fire?” It looks like Coins will be the answer. We don’t have a lot of details just yet, but according to the release:

Amazon today announced another new way for app and game developers to make money on Kindle Fire—introducing Amazon Coins—the new virtual currency for purchasing apps, games and in-app items on Kindle Fire.

When Amazon Coins launches in the U.S. this May, Amazon will give customers tens of millions of dollars’ worth of free Amazon Coins to spend on developers’ apps on Kindle Fire in the Amazon Appstore.

Amazon will also make it quick and easy for customers to buy additional Amazon Coins using their Amazon accounts.

I don’t know about you, but I’m loving that part about Amazon giving its customers  “free Amazon Coins to spend.” In fact, I’m wondering if those Coins will replace the current free app credit you can sometimes get by making associated purchases.

Coins will launch in May, and I’ll be interested to see more details. To make this truly useful for parents, there will need to be some way to lock down a credit card, so that kids can only use Coins to make purchases. I wonder if they’ll do that … and how it’ll work if they do.

If nothing else, the Amazon Coins look like they’ll be a lot of fun. And don’t forget, app developers: You have until April 25 to get your apps ready and approved for the new Coins system.