Hi Stanley,

It's cheaper to make sensors that are "dumb." This also gives freedom to the user to use the sensors however they choose. Most sensors give a raw analog output, so an ADC and a uC of some sort will be required to get any meaningful output.

Just because a sensor can be controlled with a PIC doesn't mean it HAS to be controlled by a PIC. There are almost always many different ways to implement something.

Even the simplest sensor requires a fair amount of data processing. The two you listed, ultrasonics and compass, I would put at the high end of required data processing (especially the compass if you're interested in more than 8 points).

Dennis