I chose to study the SQ-SEN-003P and 003PS omnidirectional tilt sensors from SignalQuest.

Get the datasheet here.

Looking at page six, I noticed a very clear caution to not enable weak pull-ups when connecting to the pic's input port. Yeargh. First, I recognized the term "pull-up" from Tom's class, but had never heard it used in relation to the microcontroller. A bit of time at the search engine showed that all the datasheet meant was that if the tilt sensor were connected to a port B, to make sure that that port is not set to low. Since the sensor operates on such a low current (0.25 mu amps), that setting the pin to low might not allow enough current through to power the sensor.

Also on page six, I found it interesting that there is no lead that connects to power. You solder directly to the gold sensor body.

Here is a graph of the sample output:

An important feature of this tilt sensor is that once motion has stopped and the sensor is at rest (the "reset" part of the graph), it rests in an open OR a closed position. Therefore, the transitions and not the state of the switch are most important.