Client tracking + web port + mobile portal

We are looking to build a front end with a database backend to track our clients subscription terms and contract periods. we need to be able to track our clients subscription terms basicaly a contract start date and end date. also wed like to track what product they are subscribed to and have the system send them an expiration email before the end of their term. we like the client to be able access the portal via their mobile phone and a unique link uuid perhaps to connect directly to their user account and see their information, wed also like to modify the system as need be and add more features,