New Payment Gateway Addon for Magento

Hello We need an addon to be able to install a new payment gateway service (Cardipay) for Magento script. The payment gateway's technical documentation is attached. We will need a simple page in admin side to setup the ID boutique and other variables required by the payment gateway Of course after the customer is redirected to our magento shop, his order status should be updated accroding to result of payment page, and also transaction reference will have to be saved in order info along with date/time and other variables that can be useful. And additionaly to that we will need that you ensure that you only accept variables coming back from the payment gateway's server's IP address to secure and avoid faking a payment confirmation. We have this addon already developed for Oscommerce and x-cart if you need it as sample/help code. If any questions plz PM Thank you in advance Swateam