Google has added a new tab to its Search application. Dubbed Personal, the tab shows personalized search results from other Google Services that the user has subscribed to, including Gmail, Google Calendar, and Google+.
Using the feature, I could search for my emails and photos (stored in Google photos). And as you can see in the screenshot below, the results are private, unless you explicitly make them public.
The functionality is live for both desktop and mobile clients of the service. If the Personal tab doesn't show up straight away, you can try finding it in the More menu.