The Wiimote now has a fishing pole extension to add some excitement to your favorite fishing games. Simply clamp the attachment onto the Wiimote and cast, wait...catch!
The bad news is that most of the fishing games already released have not gotten the best reviews. They are fairly dull right now and I'm not sure a Wiimote attachment will fix that, but it might add a new aspect to the games.
Bass Fishing Wii and Rapalla Tournament Fishing are a few of the choices you will have but I think that if this takes off, you'll see more releases with fishing in mind.
I can't say fishing gives you any exercise outside of maybe a few arm extensions, but if you can fish on a rainy day and spend a bit of time practicing your timing with games, maybe it can improve your talents a bit for when you head out to the real lake.
When that expert fisher standing next to you says, "nice cast!" you can inform them that you honed your skills on the Wii.