This tool is meant to show the end user the attack surface that a given device is susceptible to. In implementing these checks we attempt to minimize or eliminate both false positives/false negatives without negatively affecting system stability. The application is open source and you can contribute or review the source code at https://github.com/nowsecure/android-vts.
When a vulnerability is discovered, Google receives word and applies a patch to Android. The Nexus devices are usually the devices that receive these patches quickest as they deviate the least (read: not all) from AOSP (Android Open Source Project – The core of Android, where Google commits to). The lag time between learning about a bug and the time when a patch is applied to a device can still be significant (for OEMs, it can be > 1 year or never). For example, the futex bug (CVE-2014-3153/Towelroot) was known about in late May, early June. This bug took multiple months to get patched on the flagship (at the time) Nexus 5. This leaves users extremely vulnerable to attack from applications. Users mostly do not know that their devices are vulnerable and this tool is meant to give visibility into the vulnerabilities a given device is susceptible to.
VTS for Android devices can be used to check whether the hand was threatened recently exposed security vulnerabilities, for those who want to ensure the safety of the situation, it would be very useful.