I agree with Diogenes.
I think this is the perception for many people still in college that are applying to medical school. I can only speak for myself but when I was in college I was worried about having a backup plan. I guess at that point I felt that if I couldn't start med school right after college I was a failure and that I needed to do something else hence I needed a backup plan. I soon realized though that its never too late in life to do what you want and that it really wasn't imperative that I go to medical school right away. Stories of people going to med school in their late 20's and even 30's amazed me but also helped me see how if you really want something you should always go for it despite the circumstances. I'm just over a year out of college now and not only have I matured quite a bit, but my perceptions of a lot of things have changed too.
Originally my backup was to enter a Master's program but I realized quickly I had no interest in doing so and hardly needed one anyway. I thought it foolish to committ to two years of that. Perhaps some of you are thinking about one now.
My primary plan and "back up plan" became medical school. I'm just going to keep trying till I get in. I want to become a physician, there is no backup or substitute for me. I can't see myself doing anything else. In the meantime, I get by, I work but I think it's great. What I do now is certainly not a career but it does a good job of filling in the gap in my education.
Instead of formulating a backup plan, I would suggest finding something to do in the mean time as you apply until you get in. Try finding a job, work for a little bit, save up some cash and just live outside of academia for perhaps the first time in your lives. I'm actually glad I didn't get in a year ago, it was a blessing in disguise.