I've used an Ion Speed Pro since July 2016. Good for the money. Same form factor as the Contour Roam -- solid cylinder. Weatherproof as-is, with the rear cap in place. It's held up fine through several rainy rides.

Good daylight performance, but mediocre nighttime performance -- high ISO noise, poor dynamic range.

I'd rather have less of a wide angle lens. The near fisheye effect is best suited to action cam use at close range. For traffic documentation I'd rather have something closer to a 24-28mm lens on a 35mm/full frame digital camera. The ultra wide lenses don't capture enough fine detail at the periphery so even in daylight it doesn't always snag full license plate details. A higher true native resolution sensor would help but that increases the cost.

Runs 90 minutes. If I need to run longer I'll hook up an external battery. That requires removing the rear cap and compromising watertight integrity, so it's usable only on dry rides.

While I have run the camera with a small USB battery attached to my helmet, it's heavy and awkward -- I used rubber bands or elastic ponytail bands to strap the small battery to the Ion Speed Pro. Usually I run a small pouch Velcro'd across the handlebar with a USB cord running to the camera, mounted on the handlebar on my hybrid or stem on my road bike.

Not the most elegant solution if you need more than 90 minutes run time. But the Ions cost well under $100 and are tough,reliable and weatherproof.