The app delivers on its promise to have a very low impact on battery life, basically because it does nothing at all. Upon investigation by Android Police, it was discovered that Virus Shield doesn't contain any security-related features at all.
Android Police's writer downloaded the app and decompiled it, which is pretty easy to do in Android with standard developer tools. What he found was that the app did have some of the features promised -- but basically just the ones that had nothing to do with security.The success of this scam app raises new questions about Google's pre-screening of Play Store apps. While the search giant does a pretty good job at keeping malware out, it seems harsher control is needed to prevent such obvious fraud attempts from hitting the app store.
It's true it had no ads, and it likely used next to no battery life.
The issue was that it used next to no battery life because it was quite-literally doing nothing. The app appeared to have no real security features whatsoever, just feel-good 100-percent digital snakeoil.