Magento - Create a REST API

Hello, We have a custom build portable eCommerce system that can be integrated on any place like facebook, webpage etc. lets call it MyCart. We have a number of customers with existing Magento installations that would like to use MyCart as an extension of Magento We are looking for a Web Service using a REST/API that we can install in customer sites. The MyCart store would be configured to optionally pull all inventory from Magento and also to send Orders to Magento for fulfillment. Requirements. Data must be transferred in JSON format Inventory is pulled from Magento. Need the ability to control what inventory is made available to Owjo store. Web Service must create Orders and Customer records in Magento when notified of processed orders. People with Magento implementations and custom development experience preferred. Full details of the system will be given for selected candidates.