I poked around on the Internet, looking for a digital thermometer. I found one that had features and a price I liked, and sent the site to my wife. I was just suggesting that we needed something like the one I had found. It happened to be offered by Target in conjunction with Amazon.com.
A few days later I came home from work, and there was a package sitting by my computer. Cool! A digital thermometer. It was a bit over twenty bucks. Not bad.
Of course, we happened to be in the southern part of Santa Cruz county about a week later, and after lunch went to.... Target. The thermometer was there, and not surprisingly a bit cheaper. No shipping charges. Ahem.
The price of these things makes them very practical for most beginning barbecue cooks. From the stuff I have watched on YouTube (and I recommend studying barbecue on YouTube) lots of serious barbecue cooks with considerable experience also rely on these things.
Other forms of thermometers are also available, and for very little money. I will work with what I have right now, but may try other models from time to time. I currently have a small dial thermometer that gives me a reading of chamber temperature, but it is graduated rather generally. I think I might go for a larger dial and more accurate graduations in the not too distant future. At only five or six bucks, it seems a good investment.