You can probably just use one of the fitness bracelets (Fitbit style) and sync them to your phone. I don't know how reliable they are, but one of their explicit purposes is recording your heart rate during exercise.
Losing the heart rate connection for a few seconds during exercising isn't a big deal.
The old tech with chest straps certainly loses signals from time to time. I'm not sure about the newer tech, but I would doubt that you get cheap tech that doesn't from time to time loses track of the pulse.
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