What do you guys use to alert you of a power outage

Hi all, I put some more thought into this last night and I plan to build the same device Cobra has posted as I all need is an audrino relay which is cost's @ £5 for 2 on amazon.

TeOhk 2 Pcs User-Friendly 1 Way Relay Module Fault-Tolerant Design high Low Level Relay Module for Arduino: Amazon.co.uk: DIY & Tools

I am also going to buy the ring extender, currently I don't have any z-wave devices apart from 1 NEO Cool cam water sensor which isnt being used currently, the plan is to turn this into a second power outage sensor.

I was just wondering if anyone can tell me more about the ring extender device, from what I am reading it is a Zwave extender, also how is it integrated into hubitat, can it be integrated on its own, I found a driver for it but the github link seems to be a dead link and the driver has been withdrawn.

[Withdrawn] Ring Alarm Range Extender 1st and 2nd Generation (Z-Wave Extender with Battery Backup) - Developers / Code Share - Hubitat

I do however have a C7 hub, just researching as much as I can before I pull the trigger and spend £30.