Well I would more need it for people, so the PIR sounds like something I can use. A lock box isnt going to do much in my jeep. There is no space for it anywhere either. I would rather do this PIR thing so It can atleast wake me up in the middle of the night and I can just pull out the 45 to take care of the rest lol And its a cool project! Im bored and wanna build something haha.
Id also like to put a little sub in my jeep so anything that can help keep someone from stealing it while the top is off would be great! (Even though the box would be bolted down.)
I have like 6 arduino boards just sitting around and I wanna use them, so I think the PIR sensor would work great! Does the PIR sensor form like an "invisible" line? or what? Like If I was able to see the infrared light that it emits, what would it look like?
I guess the next thing would be to order some of these and start building it!
J-M-L: That site link you gave me is almost the exact code I could use with this as well! Just would have to change out that lamp in the schematic they provide to a siren!