Too big to be one, and the readout is too small. If I had to hazard a guess, I'd say it's some sort of radio receiver (based on the speaker grills and buzzers that seem tou abound)...
Some of the comments on Pixiv seem to indicate that Kogasa is holding a short-wave radio in the first panel. Its also been tagged as "Electronic Blocking", but being unfamiliar with that sort of stuff, I'm not quite sure what that means.
Let's throw it away.Honestly, it's outright disgusting...I ate all of it already!!TrrsshhHssssDo want, do want!♡Kogasa~ I made some yogurt sprinkled with soybean powder. Wanna eat?Umm...It's rather floury...?Chrnch
ChrnchDon't use me as a guinea pig to confirm this!!That bad?It feels like I'm eating wood powder...As I thought, two-year-old soybean powder is no longer good...