Hi, There are very sensitive touch sensors that are used in "3D profiling" of objects by an X-Y-Z- controlled machine. I believe they have a small metal bar with one end in a metal piece that is VERY close in diameter, so that 1/1000 of an inch or so deflection makes contact. Are you thinking of fabricating stuff or do you want off-the-shelf sensors?
I bet others here will have more/better ideas...