This is vaguely similar to how the NovaDreamer works. The signal is given from the outside while you’re sleeping and you train yourself to recognize the signal and then do a reality check. Its a good idea but just remember that its a method that still requires effort and training to make useful. Most likely, though there are always exceptions, its not something thats going to work the first time and then be consistent.
Ive never tried this myself but I am sure that if you keep doing your reality checks at the hourly beeps and the beep of your watch is loud enough to be percieved while you dream, that you’ll be successful.
I think there are even some PC programs out there that will issue beeps that you can alter for your own level of audibility… programs created specifically for cueing LDs.