I know a couple of options... A friend of mine at Techark Solutions created "Gift Cards" in the app Store, since the WP7 platform days:
Then, of course, there's Microsoft's built-in "Wallet" to which you can add credit cards, loyalty cards, membership cards, coupons, and certain gift cards. It integrates with other apps, too.
Techark Solutions "Gift Cards":
"Gift Cards allows you to store your entire gift card collection for convenient retrieval and tracking! I lost several gift cards earlier this year and that prompted the idea. If I had this app, I could have gotten my cards re-issued using the card numbers.
- Don't let those valuable gift cards expire
- Track all the balances and transactions in this easy to use app
- Take pictures of your gift cards to capture the important data
- Use the stored information to report a lost or stolen card
- Maintain a running balance of all your gift cards
- Supports various currency symbols based on region
- Track the transactions for each card for various expenses
- Take photos of front and back of each card for faster data entry
"