In terms of choosing the best car alarm, the abovementioned tips for remote car starters including buying from a reliable manufacturer, asking about warranty, and choosing professional installation also apply. But since these are essentially two different devices, their desirable features will be different, too.
The bottom line: Buy your remote car starter and car alarm with a reputable manufacturer putting its brand on the product. Buy it from a specialist shop that will provide the standard warranty, the experienced staff for its installation, and the after-installation services!
Look for a remote car starter with a fully functional engine speed sensor, which obviously monitors the engine’s revolution per minute (RPM). The device should be able to accurately detect the engine’s RPM to ensure that, indeed, it has started or that the engine has the appropriate RPM lest it goes into over-revolution, thus, resulting in its damage.