How difficult would it be to build a display to receive data from a digital IR thermometer that is capable of sending to a smart phone via bluetooth? Thank you in advance for any information you are able to share.
Depending on what you want to do exactly and your skill level it can range from very easy to nigh impossible.
Thr first thing you need is an IR temp sensor that can talk to Arduino. Once you have that, the rest is easy.
OK, the problem as ever with this sort of question is that you have not specified what a "a digital IR thermometer" actually is in your imagination. 
If you actually have a digital IR thermometer which provides a serial data output (like a GPS module for example), then that would be relatively easy. If however, it is one of these:
with an LCD display, then you have no data output (as far as we know about these devices), just an LCD display from which it is well-nigh impossible to extract data.
So if you fancy coming back with some genuine information about what you want to do, we can talk. 
Fair enough. I am have many years of experience in electronics but have only recently gotten involved in Arduino. Have built a few projects with little difficulty. I'm just now aware of all the capabilities of the Arduino.
I am looking at a thermometer that is capable of sending the data via bluetooth to a smart phone app. I thought that might be the easiest way to proceed.
What I actually need in the final build is 4 thermometers that will be monitored by an Arduino that will sound an alarm if any of the individual temperatures vary by more than + - 3 degrees F.
I just figured that part is easy if I can just get them communicating.
Does that make sense or is there a better way to accomplish the same thing? I would like to avoid having to run cabling to each sensor. The wireless solution makes the installation much cleaner.
What do you think?
Thanks
Ravelsnorts:
I am looking at a thermometer that is capable of sending the data via Bluetooth to a smart phone app. I thought that might be the easiest way to proceed.
So this thermometer has a Bluetooth output? Have you got the datasheet for it, citing the form of the Bluetooth output?
Hi, Paul;
No, I don't have a datasheet for the thermometer. I will google it, though. Will the Arduino talk Bluetooth or do I need a special Bluetooth receiver. If so, what type? All I see are receivers for audio. Or would one of those work?
Thanks!
You need a Bluetooth module, the HC-05 is popular (note: works great with Android phones; not with newer iPhones).