CONTACT MECHANISMS
Any of the contact mechanisms below can be substituted for the push button.  The value of R1 should be 100K ohms.
ACTION
Type of switch & source
Picture 
animation if available
Normally Open 
Regular Push Button (boring) and hard to rig it to turn on with anything but a finger push
Normally Open
This Motion Detector is made by balancing a very Unstable Weight on spring.  It is suprisingly, VERY Sensitive 
Normally Open
pendulum is not as sensitive, but easier to build

Just use it upside down
Normally Open
metal contact bar passing springs attached to non metal support. 
Use on door or drawer.
Get springs from dead keyboards or cheap ball point pens
either the spring support or metal bar can slide
Normally Open 
mercury tilt switch - a bit of mercury connects wires if it is tilted one direction, disconnects if tilted the other direction.  Available in old thermostats. 
Normally Open 
microswitch -  available free from busted mice.  New cost $3 to $4  US. 
one connector acts as N.O. and other is N.C.
C refers to common wire, connected to both.
Normally Open
coin passing  contacts