I'm aware that this is about REST, but I faced the same question on Android, so I'll post my solution here, it might be helpful to someone.
You need to treat Blood Pressure same as you treat other info you're pulling from Google Fit (i.e Steps, Weight...).
You need to add the following line to your fitness builder:
FitnessOptions fitnessOptions = FitnessOptions.builder()
------> .addDataType(HealthDataTypes.AGGREGATE_BLOOD_PRESSURE_SUMMARY, FitnessOptions.ACCESS_READ)
.addDataType(DataType.TYPE_WEIGHT, FitnessOptions.ACCESS_READ)
.addDataType(DataType.TYPE_STEP_COUNT_DELTA, FitnessOptions.ACCESS_READ)
.build();
And when you need to query it, use the following HealthDataType:
public Task<DataReadResponse> queryBloodPressureData(Activity activity, GoogleSignInAccount account) {
return Fitness.getHistoryClient(activity, account)
.readData(new DataReadRequest.Builder()
.aggregate(HealthDataTypes.TYPE_BLOOD_PRESSURE, HealthDataTypes.AGGREGATE_BLOOD_PRESSURE_SUMMARY)
.bucketByTime(1, TimeUnit.MINUTES)
.setTimeRange(startTime, endTime, TimeUnit.MILLISECONDS)
.build()
);
}
For full details check the official documentation.