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