Along the Withings product lines is also the Blood Pressure Monitor. A portable sleeve to measure your blood pressure and via the iPhone track it - as simple as that. Optionally you can transmit the results to your doctor as well.
Fresh out of the box I "blue toothed" it to the app on the iPhone and within minutes I had my first result.
It continues to function well, however, the sleeve might be a bit tight for people with more muscular arms at first but the sleeve expands.
The only observation was the difference in heart beat compared to the scale which has consistently higher results.