In the past months i was developing provider hosted apps for Sharepoint 2013 online. Everything worked fine until i run into the following problem: in some cases for my customer it's not acceptable to start the provider hosted app from inside of Sharepoint (Site Contents / Clicking on the app's tile).
One of my tasks would be:
My customer has a corporate website (not hosted on Sharepoint). Once a form on this website is submitted by a visitor I should write an item into a Sharepoint list in the app web or the host web. Of course in this case nobody is logged in into Sharepoint, so the web part of the provider hosted app should be able to write data to a Sharepoint list without lauching it from inside Sharepoint, without a logged in user.
What do you think, is it possible? Maybe i could use app-only auth?
Thank you very much!