Recommendations for heart rate pacing with smart watch vibrations to keep below anaerobic threshold

[Azariah]

Please can someone recommend smart watches that may be suitable that you have or have tried yourself? I am having such an extremely difficult time in researching myself

I'm looking for a smart watch which:

*monitors heart rate
*has the option to vibrate when a set hr rate is reached or gone over
*and that the vibrate does not only occur after 10 minutes of inactivity, but immediately as soon as the set HR is reached
*the options for the watch to vibrate to not be limited. by this I mean that it doesnt limit from between 40-60 and 100-200. I need to atleast be able to use the numbers in between these heart rates. probably between 60-100
*accurate HR monitoring
*options to adjust vibration intensity
*option to adjust brightness on the screen and possibly turn it off/on
*no wifi
*where bluetooth can be turned on/off by myself. I can't have constant or sporadic and unknown exposure to bluetooth if it tries to sync several times throughout the day. I want it to only sync when I decide this
*preferably a small screen for smaller light exposure
*preferably slim silicon with slim/small face
*reasonably priced. I'm hoping for 200 pounds or less
*compatible with samsung galaxy s7edge or ipad 16
*being able to monitor different heart rate zones might help if possible
* possibly able to measure HRV. can someone please explain to me why this is so important?
*what can I do to find my anaerobic thresthold HR? I find the calculations I have seen previously elsewhere confusing. Is there a device that can work out things like resting HR and AT? and possibly for other zones?

Edit: without camera or any voice recognition, no alexa or siri and no built in satelite gps.