Access devices (AD) aren't fleshed out in much detail in the project description, because they can take many forms.

One example might be someone who simply wants to communicate their current location through the ZP network. Their access device could be nothing more than a GPS receiver, MCU and RF transceiver. As they come into range of a core device, their AD would broadcast their identity, current location and a timestamp.

A more likely use case would be individuals or groups wanting to communicate with other individuals or groups. For these people, a two-way pager, Peek or ZipIt form factor would make much more sense. They'd also be free to use their smart phone or a computer with either BLE 4.0 or the appropriate RF circuitry to communicate with the sub 1GHz transceiver.

For this project, although we'd like to build some devices like the aforementioned examples, the focus will be on the core device, and on creating a system and protocol that can be extended by the community. For this reason, the access devices will be simple - a modern smartphone (Android or iPhone supporting BLE 4.0) running our app and a Texas Instruments MSP430 development kit. If time allows, we will attempt to create franken-devices that work with the ZP network from host devices such as the Peek Pronto, Zipit Z2, and Motorola Advisor or T900 text pagers.

If you like this project, keep an eye out - we'll be discussing communications protocols and RF frequencies soon, and you can roll your own access device for whatever your use case may be.