(TrendHunter.com) The Vivint Car Guard is an aftermarket vehicle diagnostics tool for drivers seeking to keep an eye on the health of their car on a regular basis without having to constantly take it into the mechanic.... (TrendHunter.com) The Vivint Car Guard is an aftermarket vehicle diagnostics tool for drivers seeking to keep an eye on the health of their car on a regular basis without having to constantly take it into the mechanic....