A cheap WiFi enabled digital camera. Seriously.
Buying a smartphone means you're investing in a multi-gadget tool that does every job poorly. If you want a digital camera with WiFi capabilities, you don't buy a telephone with internet access using a tiny fixed lens and almost no buttons. You buy a camera.
There's plenty of options from Nikon, Canon, etc., new, used, with WiFi capability... and if you've already got a reasonably modern digital camera already that uses SD cards, there's even WiFi capable SD cards available. Won't give you as "big" a screen for previewing as a smartphone would, but the quality of the photos taken between the two choices will be night and day. If I'm taking photos and have to choose between the two, I want good images, not a huge preview screen.