I don’t have many details of these devices as they don’t seem to be stocked by regular parts suppliers, but are readily available on eBay and Amazon. As I understand them they are essentially a sandwich of thin-film resistive material attached to the two metal electrodes. As pressure is applied, I assume that the resistive material is compressed in a manner that reduces its resistance. I’ve attached the response curve I found for the units I used.
The mass market use case for these I believe is controls for consumer devices such as microwave ovens etc.
As it’s pressure based sensing, it doesn’t suffer the issues with moisture and humidity that seem to plague capacitive sensors. It is also more immune to RF interference as the signal voltages are much higher than capacitive sensors.
So far, the field experience with the design appears to be positive.