I've got to say, Skype truly is an amazing piece of software. True, nobody's been able to take a peek under the hood thanks to it being a closed-source program but it's freeware and has some of the best functionality and cross-platform availability of any chat/voice program to date. Additionally, it's a P2P (peer-to-peer) so it relies on servers for profile and connection data only. Bandwidth is shared amongst the network, and so far I've seen next to zero "shared bandwidth" on my machines (using NetLimiter to monitor bandwidth usage).
Loading the PDA back up with software again to make it a one-package geocaching device is a little bit of work, but it's the same software I used before. I just need to reload it again. Thanks to the largest free wireless provider in the USA linksys (joke) I can use my PDA as a cellphone too (thanks to Skype). So if I'm out caching and the phone dies or whatnot, all I need is access to a wireless network somewhere and I can call friends and family to report my successes (or lack thereof).