Zooz Zen34 (zwave, battery-powered, US). Nice new rocker switch from the smartest house. Uses the newest Z wave chip, the 700 generation (“Z wave plus V2“). Can be mounted anywhere, same size as their regular light switches. Supports multiple tap patterns. Requires a custom DTH which they provide.
2021 Update
The new platform has changed the way buttons are handled, and many of the devices described above no longer work. The most common result is that only one button will work on a multi button device.
Sometimes they will still work with the official smart lighting feature, the advanced button controller smart app, or webcore, but not always.
I’ve started a new FAQ for battery powered devices that do work with the current platform. There are only a few listed there so far, but there are some for both the US and the UK and hopefully more will be added in the future.