I would highly recommend saving up for a GoPro. Its one of those cameras that will stay with you for a long time. I used a 'keychain spy camera' in the very beginning. Only £10 from ebay. Terrible videos but cheap.
LOL, I sold one of my spare GP3BE's for $375 a couple of weeks back.
The Mobius seem to be a pretty good little camera but to get good performance when you strap it to an MR will take a bit of extra care because it is so light and you will struggle to get footage that does not have some shake in it.
I am ordering one but just to use for incidental video to compliment my GP3BE+ footage.
Did a little looking around youtube and saw a nice side by side comparison of the go pro 3 and the ion air pro (similar to the Polaroid xs100 in construction and performance). The go pro seemed to be better in low light (more details in the shadows) and underwater situations, but was a little hazy and washed out in the bright light and glares.
The Ion definitely had a sharper image in full sun and is able to automatically flip orientation when inverted. At about $150 the Ion and Xs100 are less expensive, but I am finding it difficult to find mounts or gimbals that can be outfitted onto quads or multi-rotors. If anyone has any ideas or recommendations for mounting either of these alternatives I am all ears.