Trail cameras, wal mart $28.88 each
Uses 8 AA batteries and a SD Card 16GB is more then plenty
I use these as a “silent witness” around my property to see if I have 2 legged explorers on my property also good for seeing 4 legged animals as well.
If you need instant notification Dakota Alert wireless alarm works great, for vehicle detection get the metal detection version, bury the probe in your driveway and put the receiver in your house, anytime a car goes into your driveway, you are alerted. These cost about $200 or less online
Neither require internet, wi fi, tons of wiring or IT technical support. And are easy to set up cheap to buy and work.
I know these are not exactly what you are looking for but could be an alternative to something more complex and more expensive.
We have the Dakota Alert IR detectors and they are wonderful.