Many brands of temperature probes will come with a clip that attaches to the grate of the grill. Then you pass one of the probes through the clip so that it is located close to the cook, but does not touch the metal grate. If it touches, you will get incorrect readings.
Some digital temperature devices come with only one or two probes. I do not think that is sufficient. I use a minimum of two probes for every cook (grill temp + internal meat temp). If you are cooking multiple pieces of meat, especially if they are different types or different sizes, you need extra probes. Thus, I got one with four probes.
The Fireboard is great because it will plot your temperatures throughout the cook but a unit with multiple probes is expensive.
The Meater thermometers are great as they are wireless. You do not have wires to interfere with turn meat over or moving your meat from one place to another on the grill. These are also expensive.
What you are looking for is accuracy and the ability to monitor the temperatures remotely using either a second device or your cell phone or tablet no matter what you decide to get.
Whichever device you purchase, always check its accuracy in a glass of ice water, your own oral body temperature and in boiling water. Remember that the boiling point of water differs depending on the barometric pressure, so you might get something other than 212 F/100 C. For that reason, boiling water is not great for calibration, but it will will tell you whether the device is close to accurate at near boiling. Remember that brisket cooks and pulled pork will end with temperatures just below the boiling point of water, so you need to know if your probe is accurate at that level. If you have multiple probes, be sure to check all of them.