[bsimpson]

Anything with an off-switch can be offed. Anything else can have the batter run down.

If it's a safety device on another piece of hardware, like a GPS tracker for a bike, they can always destroy the tracker separately from the item.

[saalweachter]

Yeah, but people aren't stealing a smart phone to power off and display on their mantle, or trade inert as a representational currency, and you can hardly smash the GPS out of it. People are stealing smart phones to use, or to sell to other people to use.

Local hardware access is ultimately unbeatable, but it should at least be hard.

[bsimpson]

It looks like Apple and the NYPD have been collaborating here:

http://www.theverge.com/2013/2/22/4018190/nypd-apple-squad-f...

The problem with a phone is that you can put it in airplane mode and then factory reset it. Also, it's pocketable, so it's easy to hide, even if someone found the general location of the phone.