In my book I suggested getting a mini-trampoline. They cost about $39 (the price of one month's membership at most gyms), put it in front of a TV, and while you're watching the morning or evening news, simply walk. If you have a challenge with balance, put it close to a wall, should you need support.
You don't have to do jumping jacks. Walking is the best exercise and the fountain of youth, as far as I'm concerned. Here is why I love a mini trampoline:
1) You can exercise in your underwear if your choose - or not
2) It's very low impact, so it won't crunch your hips or knees - like concrete
3) It's a great multi-tasking exercise, since you watch Tv or talk to your family while walking
4) You can walk on a trampoline any time of day or night.
5) Once you make the initial investment, it's free!
Stay in shape all year around, keep your heart and muscles strong with a mini trampoline.