Hi Peter and welcome to the Grafana forum.
We have the exact same need as you described and nearly the exact same setup, except we generally push data to Influx using Node-RED (not Telegraf). Regardless, the live streaming in Grafana you have heard about it still in beta. If you know how to do it, you can try to build the MQTT datasource plug in. I tried but never could get it. I believe we are now just a few weeks away from having the ‘official’ MQTT datasource plugin available, so if you can wait, I think this will become very simple.
Are you familiar with MQTT? It’s pretty simple to set up. Once you set up an MQTT broker, it will serve as a sort of ‘post office’ to for the various clients to publish and subscribe to. Then Grafana will be configured with the MQTT datasource with the IP address of the MQTT broker.
PS: Forgot to answer your original question…You would use Telegraf to send data to both Influx and the MQTT broker. That way you can store the data for historical viewing and stream the data (from the MQTT broker) for live streaming.