Originally Posted by
mrjim
I actually use the CycleOps PowerCal. It's an HR monitor that estimates power output. No bike mods necessary. I know it's nowhere near the accuracy of the others listed but when you consider the $100 price, I'd say it gives you a reasonable estimate of your power. It's more accurate than you might think though. Here's a review DC rainmaker did for it:
http://www.dcrainmaker.com/2012/11/c...th-review.html
+1 on the PowerCal. I'm not serious enough about power to buy anything more expensive than this. I got it for $80 on sale.