Widget: Remotely store datas

I'd like to realize a widget which saves remotely infos that user has inputed. So, I need a way to store them and associate them to the right user (so he can retrieve only his datas).

I don't want to ask him everytime his e-mail, so I'd like to retrieve his Apple ID. Is this possible? If yes, how? If not, is there another accessible solution?

Alternatively, could the widget directyl send an e-mail to the user if he prompts his email address?

Thank you