You need to develop (or find) a circuit that can do this stuff and then interface the output to the display. It's all but guaranteed that you'll be using a microcontroller.
you are not going to measure Ohms directly whilst power is connected ... dunno why you would want to you can easily work it out ... you have the volts and current displayed
easy enough to work out the resistance of the load
I have one unit smaller than either of those 2 shown
have a look at this nice unit
I have it inline to my transceiver radio gear along with one of these protector units an awesome device