If you just want to pedal to keep your legs in shape, get a trainer. A lot of people seem to think that fluid trainers (as opposed to wind trainers and mag trainers) are the best. I have seen a lot of folks tout Kurt Kinetics Trainers as being very good. With a trainer, you can read a book or watch television while you pedal. I find that without these diversions, trainers are extremely tedious.
If you want to keep everthing in shape and get the closest approximation of actual riding, get a set of rollers. They also come with a wide variety of resistance devices if you want them. With a set of rollers, you are actually riding and have to keep your balance just like when you actually ride your bike down the road. It takes a fair bit of concentration when you are using them that you probably will not be able to watch TV. You definintely cannot read a book.
You can also dress warmly and get you and the bike out of the house. I ride outside unless it snows. Our winters here in SW Ohio are a lot milder than they used to be. I guess that this is the upside to global warming
. BTW, I always wanted to have beachfront property.