I'm still waiting for the energy-harvesting, no-battery-required, versions to hit the market .. seems the technology (BTLE) is out there, but its just waiting for someone to have the balls to mass-manufacture them ..
Believe it or not, BTLE isn't a holy grail for power, batteries are still a better bet when it comes to long life. One method that might work is inductive charging, which is what the pebblebee dragon does (http://www.pebblebee.com/products/bluetooth-dragon). Also notice how big the pebblebee is too- but that's because it has many other sensors.
But yeah, there are several devices in this business, and they are all trying to do a variety of things, and energy harvesting just isn't cutting it at the moment.
I really don't think it's a matter of balls ;P