I'd prefer to do what you're doing actually !. I thought about a "Turbo Trainer" but i'm not sure if a bike frame, any bike frame, is designed for the stress produced by them.
One thing i will tell you though. "Cadence". Cadence is probably the most important part. Keeping up a comfortable "easy to maintain" rhythm. I've been doing this now for about 8 years. At the moment i cycle fifty miles a day (approx 2500 kcal burned daily).
Low to no impact cycling is far and away better, and a lot less hard work, than Jogging (it doesn't wear out the soles of your shoes either).
There is a not so obvious difference between cycling on the roads and cycling on an exercise bike though. And that's "resistence", wind reistence !. It constantly changes outdoors, whereas an exercise bike's resistence will be fixed, or can be altered but remains the same during use (I could be wrong, maybe there are more advanced exercise bikes that can auto adjust resistence during use). Anyhow, outdoors it's a constant struggle to maintain cadence with wind, gusts or a change of direction. The point is to keep cycling at the same rate of rotation no matter what the resistence is. A windy day with winds of 20 mph and gusts of 30 means, on a route which takes you in all directions, more calories will be burnt than on a day where there is for example half as much wind. Depending on what type of exercise you are doing, whether it's muscle building/toning, or just plain old calorie burning will determine how hard you think you should be working. For me it's solely for calorie/cholesterol burning.
Working your muscles means having to raise your heart rate to burn fat. But if you're just doing it to burn calories/ cholesterol then you don't actually have to work too hard at all, it just take longer. So cadence is more pertinent to my style of cycling rather than toning etc. Trying to maintain a reasonable cadence against a relatively strong wind turns the pleasure of cycling into an absolute nightmare. It's enough to make you want to give up completely !.
I can't imagine what these guys i see out on the road, in their high speed clothing, and lightweight road bikes, are thinking when they just assume they can race against the wind for 20 miles. I do know one thing though, i never see the same guy twice. I just have to assume they simply couldn't work out how people do it, gave up and went home to put their bike up for sale on Ebay.
Racing against the wind is futile !.