In reply to The Lemming:
If you get a GoPro then get lots of batteries. Then get some more!
I got a GoPro 4 for my birthday. I don't have any other video cameras to compare it with so just a few comments.
Get the app to make setting up easier - for biking having the live video feed to your phone makes getting the angle to point the camera much easier.
Get a quality memory card of at least the recommended recording speed
Figure out what resolution and aspect ratio you want to end up with. Typically the higher the resolution you want then the slower the top frame rate you get, so you might get 120fps at 720p but only 60fps at 1080p.
Get a powerful computer - video editing is very intensive, you need a beefy processor, lots of memory and a fast drive, possibly an SSD.
A continuous shot is unlikely to be interesting so you need to do some editing.
Get more batteries.
Hard to say what the battery life is since I don't record continuously, I set the camera up for one-touch start and stop and record a minute or two at a time. The camera is effectively on standby. Doing it this way and not using WiFi I'll get anywhere from half to a full day though I'll turn the camera off when I know I'm not intending to film.