When it comes to purchasing a power meter, my recommendation will always be to choose the most flexible product that your budget allows. For this reason I advise purchasing an on-bike unit that can be used both indoors and outdoors, and for training and racing. However, there are some compelling new indoor power training options that may fit your niche. Cycleops, maker of the most popular power meter, the Power Tap, has been incorporating its technology into spin cycles, and most recently, the PowerBeam Pro stationary trainer.