ecmascript:

function initialize ()
{
	tracePrint ('initialize(), description=' + description + ', enabled=' + enabled +
		', traceEnabled=' + traceEnabled);
	if (!enabled) return;
	// sensor is enabled, so force initial proximity condition
	priorDistance = distance (locationPrimary, locationSecondary);
	if      (priorDistance > proximityRangeThreshold)
        {
		isInRange     = false;
                isInRangeTime = -1;
        }
	else	
        {
        	isInRange     = true;
                isInRangeTime = 0; // TODO change to current timestamp
	}
	tracePrint ('isInRange=' + isInRange + ', distance=' + priorDistance +
		', proximityRangeThreshold=' + proximityRangeThreshold);
}
function distance (p1, p2)
{
	return Math.sqrt (
		(p2.x - p1.x) * (p2.x - p1.x) +
		(p2.y - p1.y) * (p2.y - p1.y) +
		(p2.z - p1.z) * (p2.z - p1.z));
}
function computeProximity (value, timestamp) // triggering value is unused since it comes from different sources
{
	newDistance = distance (locationPrimary, locationSecondary);
//	tracePrint ('newDistance=' + newDistance);
	// test if proximity gained
	if      ((  newDistance <  proximityRangeThreshold) &&
	         (priorDistance >= proximityRangeThreshold))
	{
		isInRange     = true;
		isInRangeTime = timestamp;
		tracePrint ('isInRange=' + isInRange + ', newDistance=' + newDistance);
	}
	// test if proximity lost
	else if ((  newDistance >  proximityRangeThreshold) &&
	         (priorDistance <= proximityRangeThreshold))
	{
		isInRange     = false;
		isInRangeTime = timestamp;
		tracePrint ('isInRange=' + isInRange + ', newDistance=' + newDistance);
	}
	priorDistance = newDistance;
}
function set_description (newDescription)
{
    description = newDescription;
    tracePrint ('description=' + description);
}
function set_locationPrimary (value, timestamp)
{
	locationPrimary = value;
	if (enabled) computeProximity (value, timestamp);
}
function set_locationSecondary (value, timestamp)
{
	locationSecondary = value;
	if (enabled) computeProximity (value, timestamp);
}
function set_proximityRangeThreshold (value, timestamp)
{
	proximityRangeThreshold = value;
}
function set_enabled (value, timestamp)
{
	enabled = value;
	initialize (timestamp);
}
function tracePrint (outputString)
{
	if (traceEnabled) Browser.println ('[RelativeProximitySensor] ' + outputString);
}
function alwaysPrint (outputString)
{
	Browser.println ('[RelativeProximitySensor] ' + outputString);
}