In reply to M0CGH:
In the early days of SOTA I experimented with a touch sensitive key that relied on contact resistance. It seemed like a good idea at the time - no contacts, no moving parts. A few activation on hot sunny days were a great success. Then the Autumn arrived. It was then, on a damp foggy day, that I discovered the weakness of that approach. The keyer went mad and it was impossible to calm it down. It was its last outing 
It remains here on the windowsill of the shack. Another heroic failure.
73
Richard
G3CWI