Send alert when switch on or off

Does anyone make a smart plug / outlet that will send an alert to the app on the user’s phone whenever a timed event happens, i.e. the switch turns on or off per a schedule?

Yes, The plugs I use have that feature. They call it simply Push Notifications. I tested it before I answered. Sends a notification to my phone when it turned off and then on, from a schedule.
The feature exist on four models that I use.
Sonoff S31
Sonoff Basic
Sonoff RFR2 and RFR3

You can get them on Amazon or from the factory in China at ITEAD.CC

The Basic, RFR2 and RFR3 are used by putting them inline on the cord, or cut an extension cord and put the ends in it.