The way I see it, the ever advancing nature of cellphones means that every couple of years, every teenager worth their weight will upgrade to a new phone. That means a huge number of very affordable phones regularly coming up for sale on every New Zealander's favourite website.
These days it is quite possible to get a phone in perfect working condition with Bluetooth, GPRS, serial / infra-red access, and so forth. What's really cool is the ability to easily interface with them from any PC, via USB, Bluetooth, serial or infra-red. The cool thing about the latter two protocols is that you can easily interface with the "low tech" serial interfaces straight from any microcontroller, making for a cheap wireless interface that covers much of New Zealand. Awesome!
Interesting Links
- Sending SMS messages from cell phones — includes AT commands
- FBus and MBus protocols of Nokia phones — includes information on how to send and receive SMS messages through them + schematics and code