One of the most difficult things to accurately measure in any DC circuit is battery health. Historically, batteries would be monitored using voltage degradation, age, visual observation of terminal position/condition, and testing the PH of the electrolyte solution for flooded cell types. All of which are okay, however time consuming and cumbersome. Also, testing the PH isn't always feasible with sealed battery construction.
The Sainsmart seems to apply a small AC "load" to the battery and monitors the response to the load through their algorithm to determine battery health without all the usual gear in tow. I have no first hand experience with the brand or this particular device, but am in a career that supports and maintains stationary batteries in the Utility and Telecom industries. I would be interested in trying one myself just to gauge its performance to a traditional battery load tester. At that price point; it'd be worth the test data.