Here's Just a little follow up info on those air-pressure switches:
They are two keyboard contacts placed together - the activation pressure can be tuned to suit its application, Kai and I experimented with both the seperator material (distance between) the contacts, and the size of the "nubbin" that concentrates the pressure on the contacts themselves. With no seperator, the nubbin can be smaller than a grain of sand - the activation pressure is incredibly small : simply blowing on the swicth would activate it, or the weight of a zip-lock bag would trigger it. If held stationary, the slightest pressure on the bag would again cause the switch to activate.
As it is, we could mount the switch between the inner and outer membranes, it is paper thin and adheres with tape. any pressure to the membrane (touch) or an increase in internal air pressure (bending of the tube) would activate it.
The other option is modifying the switch (a relatively thick seperator material and a larger nubbin) and placing it closer to the bottom of a tube - this will require some serious tuning to get it to respond to air pressure changes created by bending a tube, but is still possible.
Another good thing are the switches are very easy to make (takes some precision, but with enough people on it (2-3) we can have them built and installed for about 2 minutes a switch. AND they are ridiculously cheap - salvaged contacts, a little tape and some strips of wire - so no real cost.
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