Power meters, used by competitive cyclists to monitor their power output, often cost anywhere between $1,000 and $2,000. However, 'The Limits' power meter, devised by a pair of Scottish engineers, costs less than $400. It sits between the pedal and crank of the bike, and doesn't have to be built into a crank arm as power meters often are.
The device measures cadence and torque, and uses the data to calculate power output in real time. It is powered by a coin cell battery that should last about a year.
The advantage of this power meter is that users can use the same device for multiple bicycles for added convenience and reduced cost. As a bonus, the device creates a slight gap between the pedals and cranks, which could help alleviate knee pain.