I'd be more likely to use one that's easy to get out and set up on a whim

most abdominal contraptions are total pieces of crap. ummm, try to find Ian King's abdominal workouts or look up info from David Grisaffi for some good abdominal exercises.

This.. becuz you can feel it working... you just have to use it properly.

small footprint '

The best would be just a mat. I chose this one because it's cheapest and therefore closest to what you should get. :)

This works!

what ever you do, don't buy the ab lounge, I have one and it sucks.