Quite often I have stuff on my mind like: "Don't forget to get your tea in 8 mins" or "Call back this number in 30 mins". Sometimes, i make an appointment with an alarm in my calendar - but this is a bit of an overkill.
Based on this nice OSX Daily article which gives you an acoustic notification, if your internet connectivity is back, i adapted it slightly for my needs:
Finally I can enjoy my tea while it's still hot ;)
I encourage you to play with the command parameters and try out the following commands:
say -v Hysterical Your tea is ready say -v Whisper -r 15 I am about to kill you!