Write an iPhone application

Hi there, we need the development of a mobile application using xamarin (target platforms: iOS, Android). The application is a "nutrition diary". There are two types of users: EndUser; Operator. The end user can upload photos (or take a photo with the cam) of what he is going to eat. (REQ1.: when the user takes a photo, an overlay with an oval shape should guide the user to center the plate) and associate to it: 1) a description 2) an emotional status associated with the food (with a list of emoticon icons: happy, angry, sad...) 3) kcal (number) 4) a comment The user can see the list of what he ate in the last days in a list view (attached there is a mockup) The pictures and data of the last 2 weeks should be stored locally in the device and synced with a cloud service calling a rest api (we'll implement the services... is out of the offer). The user can search in the food list (date start- date end with a datepicker control). If the data is not present locally, the application has to call the remote service. Based on a flag associated with the user profile (the information is retrieved from the cloud), the visualization of the photos in the list should be denied (replaced with a placeholder). The user of type "Operator", can search for a specific user (using rest services) and view his nutrition diary. The operator can't add photos, but can insert comments in a specific field of existing items. This comment should be visible (not editable) from the end user. If the end user doesn't add items to the diary from a long time (configurable: number of days returned from the cloud services: out of the scope) a notification message (popup) should alert the user of this issue. We need the implementation of a login form: custom and using facebook. The user can create a new profile using a sign-on form and calling a service in the cloud (we'll implement the service). The same remote service will return the informations/profile associated with the user during the login Thank you