The Cateye Micro Wireless is quite cheap, but I recommend spending the extra $5 to get the Strada Wireless.

I have both and I believe there are two non-function-related shortcomings of the Micro:

1. The head unit doesn't fit tightly into its holder, and "buzzes" when going over rough roads. I spent a couple of dozen miles trying to track down this buzz, thinking it was my STI levers.
2. Both the head unit and the sensor are significantly larger for the Micro, compared to the Strada. The Strada is much sleeker and aesthetically pleasing. The "invisible button" design of the Strada is also very cool.

Please note that there is absolutely nothing wrong, functionally, with either the Micro or the Strada. Both meters had performed exceptionally well for me, and I had never noticed any dropped signals like I do for my Polar wireless.