Nashbar Tempo Double Wireless sensor $50 Not sure anyone can be that price.
Nashbar Tempo Double Wireless Cycling Computer

Nice large screen and does all the basics and then some.


If you want a heart rate monitor too, they now have a triple sensor model
Nashbar Tempo Triple Wireless Computer

Have 2 doubles - work great.

For what it is worth, the Cateye double wireless is on sale for $79.99 and might also be 20% off but then again, you could also use the 20% off on the $50 to make it even less.