Freeze Sensor and crawl space.

It is not recommended by SS to use the temp sensors in a crawlspace (due to colder than normal temps, and due to potential moisture).  I don't have one, but I think people use them in rooms in the house, garages, barns, motorhomes, and especially with having pets and if you have a pretty hot day, you can check on your home temp and make sure it's comfortable for them.

I'm not sure the sensor would work directly attached to a pipe - I believe it senses room temp, not the actual temp of something it's affixed to.

SS has a 60-day return policy (from the date of purchase) - if you're within that time frame, you can call and request a return label be emailed to you and you can send it back for a refund.

If you have a pipe in your crawl space, why is it not insulated?  A temp sensor can alert you if it gets to freezing (or near to freezing), but knowing that the pipe is about to freeze won't help you any unless you have a forced air heater available to combat the freezing temps.

The (new SS3) sensor can measure down to 0, which implies it will survive down to that point.  I tried one in my freezer and it worked fine, but apparently freezers dip below 0 every so often and I kept getting alerts.  Still the sensor survived just fine.  keep it from moisture though.

You can set the high and low temperatures that will trigger an alert. For example I have a sensor in my living room set to trigger if temp goes below 60F. That would let me know my furnace is out and I need to get it fixed right away BEFORE my pipes freeze. I also have alert set for over 76F, which would mean my AC is out and to call a repairman right away.
The purpose of the sensor is to warn you before your pipes freeze.

A lot of good comments in here that better help me to understand the utility of this sensor. Thanks everyone! I had a misconception on its purpose but now I have a decent idea. To answer the second post, they are indeed insulated, but I have limited understanding of exactly what the threshold would be on insulated pipes. For example, if once temps reached -10, perhaps the sensor would alert me it's time to take some sort of action like shutting off the water line and draining the pipes of water until temps warm. Clearly that was a misconception as it's been stated this thing really only works to 0°. But there were some great points about it being useful to monitor the internal house temp to offer a heads up to if your heater went out while away. For the price of the sensor, I'll just keep it. I mean it only has to work once to be worth the investment.