I have PI's EMS-HW50. I think it is great. The only problem I see with checking the connection before plugging in and believing you are safe is, that think can change without you knowing it or before you can do something. I am always plugged in when home. One winter during a snow storm at night, a tree fell on my service line to the house. It broke the service line neutral. I lost $10,000 of stuff in the house. The MH was fine. The EMS disconnected from the house because of the open neutral.
This year after being in Mission, TX for the winter, the EMS disconnected from the park service due to low voltage late at night. I just figured it was due to people using heater during the cold night we had. A few day later it did the same thing. I asked the office if they could check my spot. They did, found one side of the breakers bad. Replace breaker and all is good.
The nice thing with PI EMS is you do not have to be around monitoring the system. If something goes wrong it will disconnect you.