How to build a max distance alarm
I've been searching for an instructable that does that but couldn't find it.
The basic idea is to put a small as possible tag to something(unpowered if possible) and have another small thing that can fit in your pocket. If the tag goes more than, say, 4,5 or 6 meters away your pocket box would warn you.
I think its a great idea to protect from thieves but no idea on how could I build a device like that.