I can thoroughly recommend the NextBase 402G Professional dash cam.
It has high definition camera and GPS. It retails for around the £99 mark.
Great playback software, so you can replay your drive in the Zed and relive the journey!!
The picture quality is fantastic and has "lock" facility, to save recent footage, if you are unfortunate enough to be involved in any incident. It can also be used as a still camera.
It's small and discreet and tucks neatly behind the Zed's rear view mirror.
A good product!
It's also quite addictive to replayyour last drive, especially if its over empty B roads!!
Had mine 2 months now, with no problems.
It may not be suitable for long period, passive monitoring as it has a limited battery life.
Hope this helps.