[IamKira]

umm... okkk?... if you are trying to figure out this for yourself, why don't u just use a microphone? *her voice should be distinguishable for you.. my suggestion: google audio surveillance
there will not be a camera system that can record video all day long without some giant storage device for all the info... depending on the type of shell for the file, audio files are generally 1/4 or 1/5 the size of video files which will reduce the need for storage device on your son..

that is if u are adamant about it being on him. could be better just to set up multiple wires around the house. it'll be easier i assure you