Iris smart fob

There are many alternative devices listed in the buttons FAQ. (This is a clickable link) some of the devices listed there are mains powered, some are battery powered, so with the descriptions carefully.

The FAQ thread itself is just a list of devices. If you have any follow-up questions on any of the specific devices there, ask in the device threads. Often those are linked to from the FAQ post.

You made also take a look at the following recent thread: