'I was planning on using the Puck BTW'
See comments in the destination link below:
Jon, @user106970 it would make sense to start a unique new thread for future answers. This thread was intended to describe an idea, and we have now inadvertantly hijacked this one. @allObjects started a new thread see #133 link to handle general observations using the same technique you were after. There is a lengthy discussion on pin sourcing for the nRF52 (Puck) chips.
Thanks - and yes, that's the correct GSR device. I've got no shortage on pins I can use for this (as there isn't going to be anything else connected to the espruino). I was planning on using the Puck BTW.
Yes, my vision started to blur a little when investigating skin capacitance too! I guess all I really need is for a reliably measurable change in capacitance as the skin gets sweatier - it doesn't need to be linear, it just needs a cut-off point where it sends an alert. So I think I'll try that first in the interests of reducing the number of components available to stick into my poor patient zero!
Thanks again to both of you! I'll let you know what works.