Plugin for digital product download link by email?

On my site I want to offer a digital product to people who enter their name, email address and perhaps a few other fields. After completing the form the system sends an email with a unique download link.

What is the best way to accomplish this? Is there a WordPress plugin that does it? Do any of the shopping cart plugins have this type of “register to download form” included?

I’ve found a few commercial PHP scripts that claim to do something like this, like eFormPrime, but they look a bit old and dodgy.