Buy.com offers the Kensington BungeeAir Wireless Security Tether & Battery for iPhone, model no. K39291US, for $54.99 with free shipping. (Amazon offers it for the same price). That's the lowest total price we could find by $5. This iPhone security kit comes with a wireless security tether, battery, and case. When your phone and BungeeAir keyfob are separated, your phone will lock automatically and send an alert to your keyfob.