• must be weatherproof
• must be light and compact so that it doesn't weigh too heavily if mounted on one side of my cycling helmet
• must have a user-replaceable battery (or at a push, at least have an option to replace the battery at reasonable cost/turnaround)
• must be able to connect to it using a smartphone in order to change settings and/or preview what the camera is seeing
• must be able to do 60 frames-per-second HD
• must be able to record usable footage after dark (in street lighting)

I have been using Garmin Virbs on the front and rear of my bike. I picked up the basic model for about $100. It does not tether to a smart phone, but I am not sure why you would want that. With the Virb it is easy to tell if you are recording by just feeling the big switch position and how often do you really need to access settings and make adjustments remotely, just saying. It will record usable footage in the dark ASSUMING you are using good bike lights, which you should be using anyway if you are riding in the dark. Besides those two points, the Virb satisfies the rest of the points. And some pics: