Attach the PowerTap P2 pedals to your bike and ride away measuring watts. PowerTap made a splash with the previous iteration, the P1, thanks to its simple installation. All you need is an Allen key. The P2 pedals build on the previous model and its dual-sided power measurement. But the new pedals are lighter, weighing under 400 g. And the pedals have a 33-percent boost in battery life, letting cyclists use them for up to 80 hours at a time. PowerTap released the P2 last week for $900.