Check out this timeline: On December 29th RunKeeper Pro is  announced as one of Apple’s Top Grossing Apps; on December 30th RunKeeper announces that RunKeeper Pro ($9.99) will be free for the month of January; on January 3rd RunKeeper Pro (now free) hits the fifth ranked app in the entire app store and exceeds over 1 million downloads in four days; and yesterday, RunKeeper announces the RunKeeper Pro will now be free FOR LIFE.

Now I have come to expect crazy things from the RunKeeper crew from watching them over the past year, but this certainly shakes things up. What do they have up their sleeve, that they can now offer a product that’s is certainly a big chunk of their revenues, for free? What about a single fitness platform – the fitness platform – for all others to build off from?

RunKeeper is said to be launching an API this year, which will enable developers to build off and leverage RK’s data. This will lead to numerous partnerships and is a big money maker. RK also just raised a round of funding, and continues to bring in revenue with its RunKeeeper Elite program and training programs. I’m sure they have plenty of runway and will wow us in the coming months.

We are very excited to watch this company grow and expect BIG things from them in 2011.