In this log I'll outline the PCB work I'll need to move this project along, as suggested in this HAD post, although the dog makes my case fairly eloquently already :)
There will be two separate boards for this projects, which I'm going to call the master and slave. I'm not sure how I'll design the master board yet. It may be an expensive but easy arduino+GPS+SD Card stack, a nice custom board or (the option I'm leaning toward for now) AA simpler board that plugs into a phones earphone socket and offloads the hard work of logging, GPS, UI to the phone. I think this last idea would be best as it will keep costs very low and allow me to get started without waiting 2 months for a GPS breakout board. If I go with this option, I'll just need a fairly small PCB with a few IR LEDs and IR recievers (like those in DVD players, which have some extra circuitry built in to make life easy), a micro (probably an ATtiny85 just to be consistent) and a battery connector.
The 'slaves' will be easier. Each one will be an ATtiny85, a boost converter to power from a AA battery, an IR LED/reciever pair, an electret microphone with a preamp (1 transistor, some resistors), an RGB LED for status info, a push button or two for input (may need a shift register if I go with two buttons and an RGB LED, but I'll try to get away with just the pins available) and a battery holder.
Since the whole goal of this project is to keep everything small, cheap and robust, some professionally made PCBs will be a much better fit than my usual messy protoboard mashups, and if I ever plan on selling these having some nice purple prototypes would be useful ;)