I remember the idea of "cellphone as a server" being around as far back as in Symbian times. Nokia Mobile Web Server, more than just an idea, actually was an Apache port capable of loading modules and running Python scripts on your phone (e.g. in order to access the camera) and serve dynamic pages on your DDNS-reachable mymobilesite.com subdomain.

The original project website appears to have been axed, but there's still traces of people who used to talk about it: http://www.allaboutsymbian.com/features/item/Previewing_Noki...

>MWS, in its default install, comes with a default pre-configured web site which has a number of functions, including a guestbook, a blog, the ability to send SMS messages to the phone, share Calendar information, view contact information and access the phone's camera.

I've tried using a phone as a server in a similar fashion in the past, and found it to be too unstable and unreliable. With a Pi (at least, any Pi made since the Model B+ revision) stability and robustness is not an issue, however I've tried repurposing several Android devices from various manufacturers and they always end up rebooting themselves at inopportune times, or locking up, or the server app I'm using constantly crashes. By contrast, I've had the same RPi 3 running nonstop for nearly a year as a camera server.

I think it's more to do with the Android OS itself rather than the hardware, but I could be wrong. It's possible the SoC was overheating on those phones from the extended duty cycles; they simply aren't designed for much more than sporadic use.

Can I create script which snaps a photo let's say every minute? Basically, is camera available through terminal?

Yes. https://termux.com/add-on-api.html#termux-camera-photo

I use it for git repository hosting and I like its power efficiency.