Are wireless WiFi meat thermometers actually accurate?

The better ones are. Several models in this category advertise ±0.5°F NIST-certified accuracy, and specialist-community reviewers generally confirm the internal meat readings track well against instant-read references. The recurring caveat across communities is ambient (grill/smoker) temperature readings, which reviewers say can drift on more than one wireless model, so use a dedicated pit probe if pit accuracy is critical.