iOS data entry app via an API - XML HTTP POST

I am looking to have an iOS data entry application built. Communication - The app should communicate to a remote API by sending an XML string via HTTPS POST. The remote API then responds with an XML string to the app. Data within the app does not need to be stored as XML, however, it needs to be converted to an XML string to send via HTTPS POST when communicating with the API. Functions - PIN number screen lock Sync function - sends a version number to the API, the API responds with a series of XML files. Some of the values of the child elements of the XML files link some XML files to each other - similar to how tables in databases work. The values of the XML files need to be stored locally on the app (i.e. database), however, they do not need to be stored as XML. Settings page - edit username/password of API access, change pin, default/favourite settings options, wipe all data Version check - communicate with remote server to check current app version. If the version is not up to date then either certain functions of the app will be disabled or the whole app will be disabled Data entry- 1 dynamic form that automatically displays or hides some fields depending on whether some values have been selected or not. The field names and values of the form come from the locally stored synced values / database. The entered data is stored locally on the app until the user uploads the data. When the data is saved locally (before upload), it can be edited or deleted. The uploaded data needs to be sent as an XML string via a HTTPS POST request.