If you want to take a temporary photo with your iPhone, and not have to remember to delete it from your Photo Library later one, use the Notes app instead. You can take a photo right from the app, and it will appear in the current note, but not your Photo Library. You can then delete the photo from the Note, or the entire note.
A new feature in macOS Sierra and iOS 10 is the ability to collaborate with more than one person in the Notes app. You can create a note and then add other Apple IDs to share the note with. Each person can add and edit the note in real time, or as an ongoing collaboration.
A new feature in Mac OS X 10.11.4 and iOS 9.3 allows you to lock some or all of your notes in the Notes app. You can assign a single password that works for all locked notes in your iCloud account. You can lock and remove the lock on notes on your Mac, iPad or iPhone. This provides an extra layer of security if you store sensitive information in some of your notes.
The Notes app in El Capitan adds all sorts of new features such as checklists, styles and attachments. You can import photos, documents and other files into a note. You can even add web and map links. A new media browser in Notes allows you to view all of the items attached to all of your notes.