Cameras that integrate well with phones already exist. I have a Sony camera that can:

* Wirelessly transfer images to my phone using wifi-direct.

* Do so with a tap, as it has an embedded NFC tag.

* Be remotely controlled by my phone, including a laggy but usable viewfinder display on my phone screen. This mode also automatically transfers pictures taken to the phone.

Partially reposted from: https://news.ycombinator.com/item?id=12756662