Home Assistant can be integrated with FreshTomato. This allows you to track/monitor devices connected to the FreshTomato router. Currently, there are two known implementations of HA-FreshTomato integration.

The first implemenation is on the Home Assistant website. See this page to configure a basic setup:

https://www.home-assistant.io/integrations/tomato/

This integration is confirmed to work with FreshTomato (ARM) since r2020.8. However, this implementation has a large limitation.

Excerpt from the webpage:
This particular Tomato integration allows one to track devices which are connected to a wireless router that is running Tomato as firmware. Because of a limitation in Tomato’s API, this integration will only track wireless devices.

While the contributor's code is greatly appreciated, technically speaking, the above statement is only partly correct. It's not so much a FreshTomato limitation that prevents wireless clients from being tracked. It's more the way the integration code was written.

The other HA implementation, ha-freshtomato may work better. It tracks both wired and wireless clients. It also appears to add more functionality.

https://github.com/mx5gr/ha-freshtomato

* ha-freshtomato is courtesy of Github user jakub-medrzak.