Android Question SOLVED - MQTT Polling of devices

I was wondering if folk out there had some useful ideas about how to poll devices such as ESP chips to ensure that they are still live via MQTT.

I am in the process of writing something involving a timer which sends out a "What's your status" message to all registered devices and then waits a while to see if a reply is received or not, but I was wondering if there were more elegant techniques that people were aware of.

Thanks.

JMB