CardioTrainer Pro is chock full of features.

Looking for a really good fitness application for your phone can be a pain in the butt--and exhausting. At which point, you're done trying. The GPS is off by (insert miles here), Facebook integration doesn't work, it has less than a handful of workout scenarios, no customization...

CardioTrainer has been in the top-apps list in the Android Market since the market was first introduced. CNET reviewed the lite version in May 2009, and a lot of bugs have been fixed in those two years--I mean, you'd hope so right

On Amazon's Appstore for Android you can download the full, ad-free version of the Pro version (typically $9.99) for nothing. Features include auto-mapping, six levels of interval training, 20 levels of difficulty, audio and video feedback during workouts, pedometer, more than 40 different preinstalled workouts to choose from, and a built-in music player. There's a customization setting if your workout isn't in the predefined list.

There is a precursor to installing this app on Amazon, however. You must download and install the free (or lite) version of CardioTrainer first. Once that's done, download and install the Pro version. And there you go! Unlocked, free and fully-featured.

CardioTrainer Pro will be Amazon's free App of the Day until 3 a.m. ET/12 a.m. PT tonight. Try it out. There's always the option of uninstalling if it doesn't suit your needs, and free is free.