Go to online communities that you think would benefit from the hardware. Don't sell it by posting "I have this idea <xyz>. What do you think?" or "would you like <abc>?". Listen to the problems being discussed and contribute. If people talk about problems your hardware would solve, you have an audience.

Share your thoughts in those comment sections; if they're well received, that's a positive signal.

I ran this with a previous SaaS product, which helped me get early users. Seemed like others should need to write the same tool, so I open-sourced it -> https://github.com/obris-dev/openmagpie

Understanding the problems related to your solution and who's asking the questions also becomes a conversation starter for cold outreach later.