Yep, this can absolutely be done. Home wall chargers are just a fancy switch[1], you just need a way to enable/disable it. Could be a feature of the charger, but in the worst case you could add your own secondary contactor that removes power from the entire charger when you don't want the car to be charging.

[1]: They also have control pins to tell the car the maximum amperage they're allowed to draw, but that's not relevant to the feature of "disable the charger when I don't want it charging"

> but what's stopping the power/timing controls from being buttons on the charger wall unit?

The car makes all the decisions about how much power to draw and when to do it. Excluding the DC super/fast chargers, the hardware on the wall is pretty "dumb".

It's been pointed out elsewhere, but remote notifications are useful so you know it's time to get out of the public charger and let somebody else in (or to go back out and check on why it's suddenly stopped charging)