..... Sometimes X10 isn't the best solution
I'd jump in with my CM15A for a solution
if it was for me. The OP didn't mention owning any other X10 devices. And since the CM15A isn't available right now... I didn't include it in any solutions. But I also don't mind using whatever is helpful and useful in my setup.
I wouldn't hesitate to use devices intended as solutions for impairments or disability's, myself. The more mainstream those devices are made the easier they are to find and the more competitive the prices will become. I also use a warning light even though I have a voice announcements with my setup (
as seen in my YouTube Video).
I even found a wireless doorbell strobe receiver that also has/works with a chimed wireless doorbell. I use the chimed receiver upstairs and the strobe doorbell receiver in my [basement] Home Theater [as watching a movie can drown out the upstairs chime]. The strobe is always an attention getter.
Whereas many of us are born with hearing issues or have hearing loss during our younger years... loss of hearing associated with age is also normal and very common. One of my favorite things about my home automation is the increased situational awareness the setup gives me. Other less automated solutions are useful too. Things like hanging or placing mirrors that extend views (or reflect a flashing light) can be useful.