There's more than just a standard GSM network powering the Ninja Tel network. Ninja Tel uses a little-known feature of Android 4.0 Ice Cream Sandwich that allows networks to route calls over GSM or onto Wi-Fi, if the Wi-Fi has been configured properly using Session Initialization Protocol (SIP) and has a SIP Server.
The phone will grant access to the vending machine in the background during the Saturday night Ninja Party, but is inactive and only on display on the Defcon floor.
Other apps include Eliot's Vending Services, which allows Ninja Phone owners to interact with the previously-mentioned vending machine at the Ninja party; the Ninja game, a customized version of junken (or ro-sham-bo for all you non-Ninjas); OKNinja, a ninja chatting service powered by AllJoyn; and a direct line to the Android IDE so that hackers can write their own apps for the phone.
The Ninja Phones can be sideloaded with standard Android apps, such as Lookout's flagship mobile security app.
Interestingly, the project could have some serious real-world implications as proof that it's possible to create small-scale alternative, private communication networks.