if it offered tactile feedback instead of beaming data to a smart phone?
You know, when it goes outside of the established parameters it shocks the user...
Shocking will only worsen the stress... but, hang on... the idea is still salvageable.
I'd reckon a more pleasant type of stimulation would better help in releasing endorphins and combat the adrenaline excess induced by stress. This approach may come with the advantages of:
# being adaptable outside the "bra only" range;
# may induce other type of releases - which the body will consume energy to replace.
(granted, using shocks may still work for some parts of the population enjoying alt.sex...)