[agarv]

It's not a phone app, but I made a web app[1] that can get pretty close[2]. From looking at the images I think the reason why other other apps don't look the same is that they try to emulate it use an ordered dither, while it looks like the Gameboy camera is either adding some randomness or noise as well. I have a Bayer (R) algorithm that adds randomness and it seems to get closer to the Gameboy camera output.

[1]https://app.dithermark.com/ [2]https://imgur.com/a/AiQa14B