I did it a couple of years ago when I had a hanging spot on my apartment patio. I simply cut a 2" hole on the bottom of a 5 gal pail, it worked well. I would like to try it again but this time I would cut the hole out of the side of the pail 2/3 from the bottom. The roots tend to grow downward and they become root bound right away. Keep them watered, sometimes twice per day.

Last year I wanted to make a small maintenance free tomato garden for my parents who don't garden. I planted them in farm bags full of homemade potting mix and set the bags on top of a wall. During the season the plants grew and draped down over the wall. All they had to do was keep them watered and pick tomatoes.

that hanging tomato thing is such a sales gimmick. You can do this with any container that you can elevate without spending the $$.