Power Meter App?

15% accuracy, might as well use a random number generator.

+- 15% error, is still pretty bad. I don't know how much better it could be than the STRAVA estimates, for average power there are usually about 50 watts low for me. Drafting, local weather variability, GPS drift, and position on the bike will all significantly affect the output.

I'd be interested to see some side by side results if someone has the time to fiddle with it. I should work a heap better than my Powercal HRM.

It obviously is too good to be true since no any application can measure these things correctly without any additional device. Good power meter can be quite expensive and a mobile application can't be even compared to them.

Those apps can't be used to measure power. Power equals to force times velocity which a phone app can't measure. Force can be mass times acceleration which means that we need a metering machine to do that.

Strava's estimated average power is quite good at estimating your effort.

Yea, Strava does ok actually - assuming there are no external factors at play such as high winds. Their data is best on climbs I've been told. But agree with others, 15% is meaningless.

15% is kinda bad, but hey, it's better than nothing.