Gift certificates not attached to user account?

Before I embark on making this work on my own, I wanted to post here to see if anybody has managed to create a Gift Certificate system that doesn't have the certificate amount associated with a user account.

We are looking to allow customers to purchase gift certificates. The recipient would receive their gift certificate, perhaps by email, perhaps as a paper certificate in the mail. The recipient would enter their gift certificate code at checkout, and the amount would be deducted from their order total. If the certificate has a balance left over afterward, they could enter the code again for a subsequent order, and the remaining balance would be deducted from that order, etc.

So, the certificate balance would be associated only with a code, not with a user account.

Has anybody manage to set something like this up using this module, or know of another module that would support that use case?

Thanks!