Hi Carol and thanks for your excellent question. While we cannot make recommendations as to manufacturer or specific model oximeters over the internet, your concern certainly warrants a helpful comment.
There are a wide variety of pulse oximeters available on the market today. Some are electronic, some are battery operated. Some have integral alarms that can be set for just those situations that you described in your post. Depending on the features you'll need, the price will vary accordingly.
I would suggest you do a GOOGLE search and put in the words pulse oximeter. You will find a plethora of choices. You should be able to easily find an oximeter that meets your needs in a price range that suits you.
For additional assistance, you may want to contact your doctor, local respiratory therapist, or medical supply house.
Please check back with us and let us know how you and your husband are doing..
All the best,
Leon (site moderator)