iPhone and iPod touch
iPhone and the Vodafone network
You can get iPhones for around $900 in NZ (eg here), but I'm not sure if they work on the Vodafone of the shelf - you may need to get them unlocked and simmed from Kiwi iPhone.
Installing MediaWiki
There seems to be no problem installing PHP5 and Apache, but I don't think anyone has been able to successfully get MySQL running on it which means we wouldn't be able to run local MediaWiki instances on it which is one of the major uses I'd have for them. If we could run our wikia setup locally from the ipod, then we could carry on with development and collaboration without a net connection.
It would be very useful to get MediaWiki working with SQLite, as MySQL is the main obstacle to using MediaWiki as a peer interface. MediaWiki could be packaged up as a tiny self-contained application if it had an SQLite database abstraction layer. It could even be modified to work without a web-server by running as a PHP daemon with a socket listener. SQLite brings us very close to the possibility of a Peerpedia implementation. See Extension talk:SQLite.php
Some useful links to find out more about iPhone hacking.