For developers, being able to make a bit of cash from your app after the user has downloaded it is wondrous — especially if the initial app download was free. Nothing like being able to, you know, pay rent, or eat.

While the iPhone has supported the idea of In-App purchase for a bit over a year now, Android has yet to adopt it.

A few third-parties have manually integrated their own payment system into their apps — but everyone reinventing the wheel for their own use is a bad idea. Not only is it a ton of leg work, but it puts the responsibility of handling the customer’s sensitive financial data in the laps of developers.

Enter Paypal.

Today, Paypal is announcing Mobile Payments Library for Android — which is exactly what it sounds like: a library for Android developers to use to integrate Paypal payments into their app. Customers get to make transactions without ever leaving the app, while developers get to accept payments without having to handle credit card info. And of course, Paypal gets their customary cut. Everyone wins.

Is it the best possible solution? Not really; it’s another third-party brought into the mix, requiring customers to have yet another account. With that said, it’s about as good as it gets until Google gets around to bringing proper In-App purchase support to the platform

You can find more information about the new library at Paypal’s freakishly-short-URL’d X.com