Dan writes:

I know you smart guys can come up with something I can use to see that
this dam thing is heating and defrosting the freezer coil.

Radio Shack sells cheap DVMs with PC interface. You can just monitor the
voltage across the defrost coil to detect whether it is on or off.

There are more clever ways to roll your own PC-interface line voltage
detector, but the Radio Shack product is just ready to go.

I've used this method to log water heater duty cycles and disprove the myth
that idling water heaters waste (any significant amount of) power.