Earlier this year, we posted a report of a camper conversion kit for the Prius, but it was a permanent alteration that cost USD $40,000. Now a removable tent extension has been developed by Habitents.
Habitents doesn't use any poles and is able to roll up small enough to store in your glove compartment - also something you don't get with a regular tent. It basically hangs off your hatchback with a couple of simple tie-downs, so it sets up easily.
A photo at the Gizmag source shows a view of the interior; the price of USD$90 could be recouped by avoiding one night in a hotel or motel. The manufacturers have a patent pending that would apply to other hatchback vehicles.
Link.
I don't think so
http://www.ebay.com.au/itm/Holden-Torana-Hatch-Hutch-/370619236151?pt=AU_Car_Parts_Accessories&hash=item564aa0bf37#ht_8089wt_1043
http://www.thetruthaboutcars.com/wp-content/uploads/2006/10/x2pn_az04222.jpg
There are a large number of hatch-back tents. My grandparents used to travel with one which was bigger than this, though also more complex. It added a small vestibule where one could stand up and change clothes while still being 'inside'.