First things first. If I want to get this done properly, I need to plan properly. To that end I've started using some "mind map" software (a fancy way of saying "spider-diagram") to lay out the various notes about this project. I've only discovered this method recently, but I'm finding it a lot more natural and adaptable than linear lists.

Version 1.0 of the list is uploaded as a graphic. Green items are the basics to cover in the prototype, yellow in the next version (an extension of the prototype really), and the third will likely need to be a wholey fresh build, built on what's learnt from the first two iterations.

A fourth version isn't mentioned, but will likely be required to tidy up the layout of adding in the additional sensors.

First stage though is finding someone with an up-to-date version of MS Word so I can use the PFC design calculator. The macros don't seem to like Open Office.