This type of unit is becoming increasingly popular.
Most of the major manufacturers now produce a unit that can be positioned this way. Up on the wall, out of reach of children and somewhere where you wont trip over it. A great place for it to be. These units are connected to a condenser unit which is usually located on the outside of the wall the unit is installed on.
You need to be aware that
the condenser unit can be quite noisy, depending on the capacity of the unit and the brand. Some are a lot quieter than others. Surprisingly this can be an issue for neighbours. On a still summers evening the, wall mounted Air Conditioning Units, can be heard quite clearly clicking off and on by neighbours who may be sleeping maybe 20 feet away. Something thats bound to create friction.
So
when you position the unit consider several things. Will the output be projected around the room its installed in? Locate it in the center of an outside wall. Above the window is a good idea. Point it at the far end of the room.
Don't put it over a seating area. The air stream and the noise can be annoying.
If you can direct the air stream through an open door at the far end of the room then you can get some added benefit throughout the house. This type of unit is designed to heat and cool. So you will use it all year round. Wonderful on a cold night. Come home, close all the doors. Turn the unit on high briefly and in 10 minutes
you will be as warm as toast. Then you can open the door and get some benefit through the rest of the house. Likewise when its stinking hot outside, just
shut all the doors and crank the machine up on its cool setting and you can be comfortable in a very short time. Then spread it through the house.

These ,wall mounted air conditioning units, are
very efficient users of energy. But like everything if you leave them on all the time you will gobble the dollars. The high end units have timers which allow them to turn on automatically at certain times of the day. Like 7 am. Enjoy your breakfast then go to school or work. The unit turns off at 8.15 am. Then at 5 pm when you are due home from work they'll kick in and give you a
nice warm...or cool home to come home to.
At last, an intelligent home, there to look after your comfort. No where are my slippers?