Making decisions based on actual power consumption

[mjaanes]

First of all: I am new to LogicMachine and so apologies if this is a rudimentary question.

I would like to program some logic (make decisions) based on the actual power consumption for certain devices/appliances.

Examples of one such need:
I would like to have a "Leave house" button at the main door which (for security reasons) should shut off several appliances in the house. However, if the dishwasher (or washing machine) is still running (i.e. drawing current), I would like to wait until e.g. 5 minutes of "no power consumption" before I switch off the actuators for these appliances

I am perfectly fine with the LUA programming part. However, I  need a piece of advice on what type of physical sensors/devices I need to buy & install nearby the appliances to be able to measure power consumption and make power consumption available to the LM5.

Thanks in advance