Thanks, missed that. I enabled Health Check and I do see the status "Online" in the Current States in your driver.
However, kkossev's Health Status app can't seem to find healthStatus state in your driver for some reason, and doesn't include it in devices available to add to his app. So this probably is a question that I should ask kkossev about. I'll hit him up.
Defining this capability also adds a ping() command, which I find very useful for checking the online status of the mains-powered devices and measuring the round-trip time.