We know you wouldn't buy the Brooklyn Bridge— though at one time, many folks believed they did.

Around 1900, con man George C. Parker sold it over and over (once for $50,000).

During that era, William McCloundy, known as "I.O.U. O'Brien," also sold the bridge, and spent two years in Sing Sing prison for his efforts.

Chances are better that you'd fall for some less-than-reliable apps that promise to monitor your heart health.

Recently, Johns Hopkins researchers published findings in JAMA Internal Medicine about a high blood pressure app they felt was dangerously inaccurate.

And although that one app was debunked, another popular app, called out in a MedPage Today article, still uses the same dubious technology. (The Food and Drug Administration doesn't regulate apps.)

The app not only promises to monitor blood pressure, heart rate, blood lipids, and blood oxygen, it also watches respiratory rate, vision, hearing, and lung capacity, and tests for autism-spectrum disorder.

If you have heart disease and want to keep tabs on it, the smart choice is a medical-quality chest-strap monitor or FDA-approved device that monitors heart rhythm.

For blood pressure the American Heart Association recommends you use a cuff-style unit for accurate readings.