Good luck with the cochlear implant. On waking devices, I use a Smart Assistant. The volume can be turned up quite LOUD. I’m probably one of the few people in the world using the H-K Invoke Cortana speaker but I’m sure an Amazon Echo Dot or Google Home Mini would do just as well. You can get an Echo Dot or a Google Home Mini on sale for $30 to $40 from time to time. They depend on being connected to a Wi-Fi router and from there to the Internet. But I’ll just say to mine, “<wakeup word>, Set an alarm for 2 pm.” A voice will confirm the alarm is set and if you’re unsure you can say, “<wakeup word>, What time is my alarm?” When the alarm goes off, you just say, “<wakeup word>, Cancel.” If you’re having trouble sleeping, “<wakeup word>, what time is it?,” etc. If I have something really important that I want to be sure I don’t miss because of an Internet glitch, a power failure, or whatnot, I also set an alarm on an old cell phone. I still have good low-frequency hearing and I turn up the volume on the cell phone to the max. I guess if one’s hearing is really bad across all frequencies, this isn’t going to be a good backup method nor is the Smart Assistant suggestion.
Another thought is to get some sort of AC-powered vibrating pad that’s comfortable enough to sleep on, plug it into a Smart Plug that can be controlled by a Smart Assistant or your smartphone and then use the vibrating pad as the alarm clock. (I never like the idea of sleeping with heating blankets, etc., that are AC-powered but I guess they’re all Underwriters’ approved and judged safe).