Agree with both of you – it'd definitely be interesting to see if there was a way for the vibration to be actuated automatically, without deliberate effort on the patient's end. I have to imagine that it can be a stressful moment for patients, so removing as many stressors as we can to streamline the process should make it more effective.
Heart rate's definitely one potential trigger. Maybe there are other triggers like weather, or time of day where episodes are likelier to occur as well?
If the device could act more like a FitBit and track some of that data, it might even be able to use historical data to more accurately identify when these freezing moments occur. And perhaps the long term vision is for the device to actually get smarter and better at identifying these freezing moments the longer patients wear it.