I decided to use a cheap 3G router from aliexpress and a cheap USB camera, claimed to work in linux.
The router has Ralink/MediaTek RT5350F inside.
The 3G router (link) took 23 days to arrive to Slovenia (EU). It cost only about 7 dollars.
This is the link mentioned in the above review.
This router is very well documented.
The bottom two images are from that link above.
It looks promising and it works!
The camera (link) works too, but it's resolution is only 640x480 :(
The image is also much closer than it actually is!
Photo album of camera: link
Unfortunately, while twisting the lenses to get a more focused picture, I broke something (??) and now all I can capture is this:
Fortunately I still have a (better) linux-compatible (I think) webcam at home.
When I'll have more time I'll install open wrt on the router and try to establish a connection with the camera.