I'd also like to hear what your idea is. I don't know of a platform to solicit someone building your device at a price you'll be wanting to pay, but there are forums to help you learn how to do it yourself if you're motivated enough.
If it's cool enough to pique interest, you could try posting the concept in an electronics community and seeing if anyone's interested in the challenge, or an ideas community and just floating it for people to choose to run with.
It's also possible the device already exists and someone can suggest an easy option for you
I think Lemmy would either need to find a way to wean Redditors off of their dopamine machine or replace that dopamine machine long-term to sustain an exodus from Reddit. Either that, or Reddit will need to break their dopamine feedback loop. There are some cracks showing, and that might have already killed the platform in the long term, but it'll keep going from pure momentum for a while. Maybe as long as months or years.
Seems like there's more sexists and racists than I used to see over there, which is definitely offputting. I've found communities that are supportive of thoughtful discussion are more appealing, and Reddit definitely lacks that lately, outside of some small, relatively niche communities.