In many countries you can ship stuff with a receipt notification for a minimal extra charge (e.g., 1-2 €). Basically, when you ship your item, a 'postcard' gets attached to it and at delivery time the recipient is asked to sign the postcard that is then returned back to the original sender.
If this system could work internationally, that would be the best option. The extra charge seems way cheaper than the cost of any infrastructure to support remote disable or remote enable.
Furthermore, the remote disable feature has a problem. It pushes people who steal items to basically learn that they simply must never upgrade. So not only you loose money, but you also end up having products around that may malfunction giving you at best a bad image and at worst real trouble.