Sammy: as you can see, my sensors are pretty big. I have used smaller ones in the past, but these are easier and last longer. I have seen the $1 ones you mentioned, but haven't tried them yet.
I need to find a source for these too, because they charge way too much for replacements ($25 + shipping for two sensor cables).
I'm going to order a Uno and try the example you linked to. I'll report back my results.
Any suggestions for a quiet beeper?
David
p.s. I have experience programming, but very little with electronics.