SUV Tents

Googled this:

Three was something about a roof tent in the latest Drive magazine for the new Forester Wilderness.

Hopefully it comes with a flexible hose that can attach to the exhaust to redirect it at the front of the car. Even if the exhaust is not inside the tent, the exhaust would be right next to the tent. Perhaps the users of such a product are warned not to run the car to use the car's heater to warm the tent, but some users will do it.

If not the intent to use the car's heater to warm the tent for safety, and just to add the cargo area of the car, just get a bigger tent.

As to what OP saw, there are lots of tents that incorporate the car. See:

specifically listing the 2006 Forester:

Thank you!