Monza submitted by Gabriel Garza is an open source script that simplifies the validation of iTunes app store purchases and subscriptions. Validation of in-app purchases should be done on your own server, and Monza simplifies the process.
Monza is Ruby based and provides methods and objects for easy checking of active subscriptions, expiry dates, see and in app transation receipts, and check if trial periods have ended.
You can find Monza on Github here.
A handy script for validating in-app purchases.