I am currently riding an exercise bike and writing this at the same time after managing to strap my laptop to the bike. Yes, the internet is indeed serious business.
A word of advice, if your exercise bike's display has even a small lip, just put the laptop on it and strap it firm with a bungie cord (available at camping shops and online) as opposed to buying an expensive contraption to secure it with.
Here's my bike, so far I really like it. You have to work on the adjustment a bit so that it won't sway at higher resistance levels, but otherwise great for a low price: