https://www.indiegogo.com/projects/trackr-bravo-the-thinnest-item-tracking-device-ever

There's also this:
 
http://www.thetileapp.com

great ideas I wonder if you put any of them inside your control cavity it would cause interference noise.

http://en.wikipedia.org/wiki/Geocoin
 
https://www.geocaching.com/
 
I have a few Geocoins but have not activated them yet. This thread may motivate me accordingly. I have held a Gauss meter to one and so far --NO reading of EMF /EMI .  I shall report back after activation.

I was discussing this yesterday with my band's keyboard player as he regularly has to leave his gear unattended before or after gigs. He said that a friend of his had a mac with some tracking software on it and it got stolen. They managed to locate the computer using the GPS tracker software but when it was reported to the police were unwilling to or were unable to get a warrant to search the premises. So was wondering how effective it would be regarding getting your stuff back if it was stolen.
 
 
(Message edited by jazzyvee on July 10, 2014)

Anecdotally having GPS tracking software in phones and computers seems to get a reasonable response from police departments here in the states. As far as musical instruments go, around here the musician usually has to do most of the leg work but the police seem willing to get involved once they have something/someone to go after.  
 
Keith