I used a Drift Ghost S HD and 4 x 64Gb SDXC cards. Used about 175GB of data or so. Considered the GoPro but the form factor is a little bulky for a helmet cam and the remote control was half the cost of the camera again, Drift bundles it free. The onbaord mic for the drift is worthless when moving though, it;s front mounted and has zero wind protection. I used an external mic mounted in the helmet, again the Drift bundles a weather resistant back cover with openings for USB/3.5MM.
As for the pictures, taken with my LG G3, really happy with how they turned out.