HA down service

Is there any way to check if my HA is down? Like today after a electrical problem at home the Raspberry Pi did startup well but the HA service is still down (Dont know why yet). Is there any kind of service i could setup to get a mail/notification that my HA is down?

For simplicity this works pretty good -> https://www.labnol.org/internet/website-uptime-monitor/21060/

If your prefer a local installation rather than a cloud service I suggest to try nagios