I have one of these
I normally leave the WiFi off, and turn it on only if I want to access the files. It then takes a couple of minutes before you can connect to it from your phone.
It saves a new file every minute. It's not so bad grabbing one or two files, but if you want several minutes worth it's easier to grab the micro-SD and connecting it to a computer
No "incidents" but I've gone through the video a couple of times to take screen-grabs such as this:
I think it's been a worthwhile purchase, mostly for the "assurance" that if I'm involved in an accident in future I have some evidence of what happened
I got front and rear cameras. I installed the front myself but have yet to install the rear. I have been reading multiple forum threads and think I've figured out how I'm going to do it.
I have mine powered on 24/7 via the OBD-II port, by making up an adapter that plugs into the OBD-II and provides a cigarette-lighter style power socket. I then simply ran the power cord along the top of the windscreen (tucked behind the headliner) and down the drivers side A-pillar.
The camera has a "parking mode" where it does not save any video if the image does not change, which means each morning the first video it records is of me opening the garage door.
I use a 64GB micro-SD and it holds around 2.5 days of (front camera) recordings. Once I hook up the (lower resolution) rear camera I expect it to hold between 1.5 and 2 days worth
The other thing to note, is that if you mount the camera behind the rearview mirror (as I have) it will have trouble receiving GPS signals - which means location and speed data isn't recorded (which I don't mind) but it also has trouble synchronising the time. Mine finally set itself to the right time after being installed for a couple of weeks.
If you mount it as high as possible on the passenger side it will have a better chance of getting GPS lock.