Sure. I work in a large university building and can power up/down various systems from my desk for the same reason. But it doesn't require a full tablet computer in each room. These are simple network addressable devices on their own VLAN that allow me to (for example) create an interface that sends a string of commands like a remote control, provided I give proper auth. If you're a regular person in any of the rooms in the building, you can't easily gain access to the VLAN, much less connect to any of the networked controllers in the rooms.

As a result, I can shut things down from my office or set up schedules to do the same. I can monitor usage and save resources (lamp hours on projectors and lighting, etc)

The idea of using a full-on tablet computer is just silly and sounds more like something I'd do while tinkering at home and was looking for a use for some old phone or tablet sitting in a drawer. It's not something I'd put in any enterprise or commercial space.

I've been in many hotels that required the key card to enable power to the room. Some hotels used a simple switch activated by presence of an object in the slot. Many could detect if the NFC tag key was present, but not read the value. Only a few I have seen actually verified that the key was the right key.

I've seen those too. They're quite inconvenient because they actively prevent you from charging your phone or laptop while out of the room. They should leave some marked outlets enabled but usually they only do so for the mini-fridge. And of course "fancy" places build that into a cabinet.

I usually have someone's business card on me, so I'll stick that in the card slot so that I can head to dinner while stuff recharges or the room cools down (for places where the A/C is tied to the same switch). I have yet to see one that's anything more than a simple mechanical switch.

Ask for two card keys and leave one in the room.

At least at the one I stayed at once, you didn't need your room card in the slot, just a card. YMMV.

Though I wouldn't be surprised that the cleaning staff would "clean" it up if you weren't there. Might want to put out the Do-Not-Disturb sign too.

The one I ran into that did that had an outlet that would work when out of the room... in the bathroom, for a rechargeable shaver, presumably. So my laptop got plugged in there...