1. 4 minute warmup - jogging in place, bending, twisting, arm circles, dancing, whatever. Slow and full body motions
2. 30 seconds: run in place. High knees, pump arms, do as many as you can in 30 seconds
3. 30 seconds: walk or jog in place
4. 30 seconds: either squats or squat jumps, as many as you can
5. 30 seconds: rest

Repeat Steps 2-4 three more times.

Total (including warmup): 12 minutes

Of course, check with your doctor, etc. etc. Make sure you're doing things with correct posture and alignment. For squats, make sure your knees don't wobble to the sides, but keep them pointing in the same direction as the big toe. Also, keep your back and neck straight.

That's a "basic" workout. It involves running and jumping. I'd alternate that with a similar routine, using pushups (knee pushups work fine to start) and pullups (you can progress to a full pullup using an inexpensive contraption called a "Jungle Gym" - visit www.FitFam.com/products for details.

And then find ways to get these basic movements - run, jump, push, pull - into your life regardless of your surroundings. Lift kids. Pick up bags of sand at Home Depot. Tie bowling balls to your golf bag. Be creative.