Hi,
I set up this integration in my home-assistant and faced the same problem.
I have found a solution for this that suits me here in the forum:
I have setup the entries that in needed as new sensor in my configuration file.
Here the REST call you postet for example written in the configuration.yaml
sensor:
- platform: rest
resource: http://eta-touch.fritz.box:8080/user/var/40/10021/0/0/12080
unique_id: eta_kessel_status
name: eta_kessel_status
value_template: '{{ value_json["eta"]["value"]["@strValue"] }}'
have a nice day.
edited link to correct post.