I’ve had a service dog for 6 years. She was originally mobility for joint pain over time her job has shifted to balance for a high heart rate and picking items up so I don’t black out. I’m on the wait list for one that will hopefully be able to do cardiac alert- alerting when my heart rate is too high or I’m unconsciously ignoring feeling like I’m about to pass out. You can sometimes get a service dog from an organization that costs nothing to a couple thousands- vs 20k+. If you can have a shedding dog your options are better. In my opinion they are 100% worth it. The only issue is that I still have to take her out when it’s 100 degrees out and it feels like my skin is being flayed off and I’m about to die from heat, but at the same time the freedom to do more actually improves my POTS

I have one for pots! And for a few other things but he helps with my pots a lot

I believe it would work. My grandson can tell when im having issues way before i notice. Non-dog recommendation. Garmin smartwatch. Forerunner 235. It has pulse rate graph for last 4 hours right on the watch. So it is available with only 2 minutes delay. Unfortunately (or fortunately), my pots symptoms have morphed so that nausea hits before the SOB and i dont notice the high pulse as quickly. Im sure newer watches offer alarms on high pulse.