when reverse-engineering cat’s toy I have found vibrations switch SW-18020P inside. It looks like useful part so I decided to buy some more. Searching eBay for “vibration switch” gives plenty of results. There are many variants with one common feature - I managed to find little to no information about them. Is there any important difference? Such as sensitivity, lifetime, rated voltage/current? How can I determine it?
Only the manufacturer can tell you the rated parameters like voltage and current.
Sensitivity and lifetime you could determine yourself using a test setup. Hardly worth the effort, as it either works in your application, or it doesn't.
The simple ones are just a ballpoint spring inside a metal tube.
The spring will contact the inside of the tube with movement.
Can be made with a piece of metal tube and a ballpoint spring, hotglued to one end of the tube.