Toyota factory security system?

[RS13]

Hi fellas,

My brother has an '05 Allex, with tv/dvd/reverse camera head unit. He pulled it out the other day to install a band expander, found an absolute shambles of wiring behind it so removed a few "unconnected" looms hanging off the back of the head unit. Goes out to the car the next morning, finds that the horn is quietly beeping away and it won't start. Plugs "unconnected" looms back in, car works perfectly again. He mentioned that he has Toyota factory security stickers on the windows.. has anyone here had any experience with these systems? Can't find much on google, would like to know exactly what they do and how they work if possible?

Cheers.