I know this is an old thread but as an engineer I have to comment. There is no way that I know of that any device can directly measure either power or force. In both cases you measure an effect that a power source or a force produces and you calculate the power or force from that something that you can measure. In this regard the PowerPod is no different from any other power meter. It is unlike the so called DFPM devices in that it does attempt to measure the effects your pedaling force produces on some structural component of your bicycle. The Powerpod measures the accelerations rather than the forces produced by pedaling and it measures wind pressure to produce a good estimate of the aerodynamic force acting on you. From those it solves the Newtonian force diagram to derive your pedaling force and calculate your power. This is a perfectly accurate procedure, the stuff of the homework questions in the back of your physics 101 textbook. Doing it in real time in the real world is trickier of course and Velocomp has developed quite a bit of intellectual property over the years to allow them to do this quite well, actually.

Is it as accurate as a DFPM (and I won't try to change that name even though it is inaccurate)? Much of the time it is! You can read DC Rainmaker's review. It is not as accurate under all conditions however. Over the years Velocomp has refined their software and have closed the gap between their product and the competing products. Clever software can do amazing things. Ultimately clever software may not be sufficient to close every gap in performance between PowerPod and the others. But it still appears to me to be a very useful product. I do not own one but I am thinking of getting one. If you need the best possible performance under the broadest range of conditions then you should consider one of the other power meters. But if you just want a power meter that you can afford and you are not doing something critical to your personal income level, like training for the TdF, then the PowerPod is well worth considering.