While I have my system being
BlueIris on a PC, I have had some experience with a HIK NVR at our shooting range where I am an RSO. Things to consider:
IF you have an incident, you will need to access the NVR and be able to find what you are looking for. Not having a screen, keyboard and mouse will make that difficult. Trying to do that on an iPhone or iPad will not be very easy. Then how are you planning to download the video of said vehicle? It takes time and bandwidth to do that. The HIK NVR takes several minutes just to spool one minute of video to a USB stick at the NVR. I am sure it would take a lot more time over a phone app. Then you have the size of that downloaded video on your phone and need to get it off.
Do you have light at the entrance? If you want metadata on the vehicle at night, you will need good lighting for that and an overview cam. Others have stated this, but I feel the need to emphasize this.
Just because you have a cam covering the road, does not mean you will get great plate caps. Especially at night, cars can 'slip through the cracks' so to speak. I often see cars on my overview cam that get no trigger on the LPR cam at night. And sometimes the overview cam misses a motorcycle, bicycle or person on foot at night. The more cams you have, the more potential you have to get a good capture. If you 'assume' that since you have only one way in/out that you do not need to plan for both directions, you have the potential for failure here. And I think it is a higher potential that you believe it to be. The last thing you want to happen is to get the neighborhood behind you on this system only to have it fail when needed most.
Don't forget to add in the hidden costs for this system. Like the HDDs, Cat cable, connectors, conduit, mounting boxes, a UPS for the NVR and if used a POE switch.