What device do I add in order to detect if my project is moved? I seem to be going round in circles trying to find the answer to this question, so thought I'd ask the good folk here.

I have an Arduino pro mini 3.3v based project, using lowpower libraries. It wakes up every h hours and takes a reading.  I would now like it to still wake up every h hours but in the meantime know whether the item (the board, or its container) has actually physically been moved - like binary, did it move or not at all?  

I don't need constant monitoring of position. Once triggered I'd turn off the interrupt until the next wake up event.

In my mind I see the solution as being an interrupt attached to low power device which when moved slightly triggers the event to be recorded.

pseudo code would be:

if ((hour == h_hour) &amp;&amp; movementDetectedSinceLastWakeup){
  doStuff();
} else {
  goBackToSleep(2hrs);
}


My question is, what kind of sensor should I consider for this job? 


3.3v 
lowpower 
can trigger interrupt


EDIT "move" as in it vibrated past some set level.
There's two basic ways of detecting vibration - one which is quantifiable and one which isn't (much).

The simplest way is a sprint (possibly weighted) inside a metal tube. Vibration causes the spring to move and touch the tube - the resultant circuit is just the same as using a button. Sensitivity can't be controlled (other than maybe "how many times in a given period does the spring touch the tube"), but it's very very simple to use. They are often used in simple movement alarms (for things like bikes, etc).

The second method is to use an accelerometer. These are harder to work with but they do give you the actual amount of vibration at any given time. They are far more sensitive than a simple spring+tube, but since they are an active component they need to be constantly queried (often through I2C or an analog input). That makes them harder to use in a low-power scenario.

Some accelerometers are more intelligent and can be programmed to trigger an interrupt when vibration above a certain level is detected, though again that increases the complexity of working with them.

So in short: the lowest power option is the simple spring+tube sensor - it uses zero quiescent current. The best option is a programmable accelerometer that can trigger an interrupt to wake the main MCU. Which you choose depends on how sensitive you need the device to be...