Daum Electronics has released the Ergo Bike Premium 8i, an exercise bike that attempts to replicate the feel of a real bike. However, the real magic happens once you take it online. Not only can you compete on virtual versions of famous courses, such as the biking portion of Hawaii's Ironman Triathlon, but you get to compete against others as well. You'll receive detailed information on everyone's heart and breath rates, and this will allow you to get a real feel for your competition.
However, I will warn you to be careful with bikes like these. Back at CES '07, I tried out a similar bike (not the 8i). And while it was 99.5% realistic, that fraction of a percent caused me to peddle much harder than necessary, and left me just short of an asthma attack. Long story short; unless you're a pro just go get a real bike, a real friend and go outside. [CNET]