As I run out of time, I'm thinking of dropping the USB capture devices - but I won't have time to develop a solution without one. (I believe something like run ridge SDK on the leopard board and a video capture module is going to take me too long.) For this year a video server is looking more feasible - but it leaves the 1-wire data logging high and dry.
So a Vivotek 8102 is on it's way for testing - "just in case".
Running an addition arm board for the 1wire is overkill and battery intensive.
At a glance standalone dataloggers are a +£50ea
good ones, (Tiny tag), +£100ea
Thinking about alternative remote 1-wire for less power consumption than an ARM board...
Ardiuno plus data logger shield (SD card + real time clock + 1 wire interface)
Given that there is already a datalogger sketch written for this, it's really tempting... but if we only need one logger per tunnel, and one exterior logger; is it worth it? Probably not... but at £30 for the base unit and £12 a sensor it might be worth a look at.
See also the SDcard libraries in this arduino weather station;