Instead of getting an exercise bike, I just bought a mag trainer for my regular bike. Now I can use that for indoor cardio, and if I want to ride outside, it takes about 20 seconds to pull the bike off of it. Add a simple bike computer to it, and you've got all you need.
This is the trainer that I got, though I'm shocked at the price, it was only 99$ when I bought it... You might find it cheaper on eBay or somewhere else.
These guys have some other trainers by the same maufacturer that are more reasonably priced, and the RDA-850 looks pretty nice. Of course if you don't have a regular bike none of this helps you...