Magento Integeration with external inventory management system (Third Party)

Hi All, I am looking for Magento Extension which will connect with third party databases to manage inventory accurately. We are a online ordering portal which partners with physical retail outlets where in we host their products on our portal which is multistore concept. On our portal customers can find their favorite retailer in their location and order products. We need to integerate our magento database backend with various third party systems (Physical retail outlets inventory management system) Once we integerate the systems we should be able to see realtime data for in stock and out of stock and everytime there is sales in retail outlet and on our portal Do let me know if you have any questions Best Regards, Abdul