Arduino laser security trip wire for my vehicle

interesting.....

So it basically only works with heated objects though? like if a stick was to fall off a tree and fall into my jeep, the sensor wouldn't trip?

AS far as the maintenance thing, whatever I use would just set in my roll bar on my jeep. It would be hard fixed so moving wouldn't be an option. Id make sure it wouldnt ha

But I am more leaning towards this PIR sensor now.....