I have the Bluetooth model and I use the app all the time -- I use it to set the time and temperature and to get alerts -- the app alerts when the water is at temperature and when the time has completed.
I periodically check the app to verify that the temperature is holding.
I wish that the app would alert me when the temp is close -- the Anova beeps when the water is within 2 or 3 degrees, but the app does not (yet).
The BT model is limited on range, but the extra dollars for the Wi-Fi was not worth it for me as I am generally within BT range -- or not out of range for very long.
I really like the Anova, but for me it's more about being able to cook things during the winter that I would normally grill (and it's too cold or too wet or too windy to grill). I have not yet found a food where the Sous Vide method is better than grilling. Then again, I have only used it twice