Device Independent centralised business application

Looking for someone to develop a set of mobile apps that run on different mobile platforms that connect to a secure central backend DB. Would prefer the same developer to create the backend and front end apps and am open to how. Needs to be held and transmitted securely. Push notifications and smtp will probably be needed. Data would be shared amongst various users on different devices as well as PC desktop devices with Outlook integration. Some configuration data would needed to be stored in a cloud. Backend would also need to do some events that will change the data. Backend may need a web based client too. Finer details will be provided on contact. Confidential project with a confidentiality agreement to be signed. Looking for someone to work with long term. Thanks.