great idea! and most importantly simple. In the past, I have made different designs for the piezo pickup. wrapping film and an elastic band for money worked effectively. But I have experienced low gain and a lot of piezo pickup noise. Now on voice recorders there is a possibility of amplification. I think to return to this idea. Might be a good idea for a video.
I’ve utilized plastic dip in place of silicone. I’ve also seen (as with piezo instrument pickups) utilizing a preamp (either with a battery, or phantom power). I see Metal Marshmallow sells kits….However I see there are similar mini preamps one can purchase. Have you delved into these shark infested waters? I’m wondering what folks have tried, and what’s more successful.