I recently done a LOT of research. It pretty quickly narrowed down to the BlackVue mentioned above or Itronics ITB100HD.
When I bought mine on weeks ago, I bought the iTronics as it was $170 compared to the $260 of the blackvue. The iTronics also takes better videos at night, much better viewing angle and is generally considered a more reliable unit. The Blackvue has a better exterior look in my opinion.
The Blackvue's used to be a lot cheaper until they did a big cut down on people selling them on eBay, as this was mostly people selling them illegally. Not fakes, just unauthorized sellers. iTronics has recently done the same thing, which their unit now being $240 on eBay.
I'd still go the iTronics over the Blackvue from everything I read online. Other than the better viewing angle, the iTronics is also very quick to delete old files when card is full with minimal recording time lost. Plenty of video's on youtube comparing the quality in night and day. iTronics (not unlike the Blackvue) has Full 1080p, GPS sensing with speed in km/h, 6 directional G-Force sensor.
Lastly, for an extra $30-40 you can get either a 'Power Magic' or an 'Uninterrupted power supply' that will cut the power off when in parking mode, if battery goes bellow a set voltage or after a set timer. Any of these will work, some have more time options, and some have more voltage options, price varies, just pick to suit.
I've never tried a cheap one from eBay. But I didn't want to hardwire something cheap and unreliable into my car. I also didn't want something massive and ugly.
(Hint: on B-series falcons buy JayCar part # PP-2066 for $4 and you can make up a plug that will plug straight into the mobile phone kit plug behind fuse panel).
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