Create Small Applications linked to various Softwares via API

What we require is the following: 1. Connect our Sales Mobile Software using its API directly with our Stock Control/ Inventory Software. Alternatively allow it to be exported via CSV and to be bulk imported every 30minutes onto the system. 2. To connect our inventory software to small applets created by the developer using the API, so that users and clerks can Add Orders, e Edit Orders and mimic the functionality of the inventory software but in segments and depending on roles. Using the Inventory software as its engine with linkages as the applets for users to edit All must be web based. 3.