It’s a config that lives in Esphome on your home assistant server. Esphome has a Web based editor with some syntax help. When you click update it compiles it for you and uploads it ota.

You can probably sample the data on the device at a much higher rate and send updates instantly if it’s over a certain threshold

I’ve got several of the AthomTech smart plugs, they run Esphome, and you can fork their firmware and modify it as you see fit. I’ve got one pinging a fairly unstable server and will power cycle it if it doesn’t get a response for 10min, all on device so it works without home assistant running.

Here’s it’s config, defaults to 10sec, but you can change that easily

github://athom-tech/athom-configs/athom-smart-plug-v2.yaml