The performance of the devices — one that relies on a chest buckle sensor and two that use seat pads — is too inconsistent, the National Highway Traffic Safety Administration said.
"These sense the presence of a child; they just don't do it reliably enough," said Kristy B. Arbogast, a researcher at the Children's Hospital of Philadelphia who tested the devices for the federal agency.
"While these devices are very well intended and we do appreciate the manufacturers and inventors, we have found a number of limitations in these devices," NHTSA Administrator David L. Strickland said. "We don't think they can be used as the only countermeasure to make sure that you don't forget your child behind in a car."
The three devices are the Suddenly Safe Pressure Pad, the ChildMinder Smart Clip System and the ChildMinder Smart Pad. There was no immediate response from the three manufacturers.
The NHTSA report said that, in some cases, spilled liquids caused malfunctions, cellphone use interfered with device signals, devices turned off and on during travel and an improperly positioned child caused seat pads to malfunction.
"In sum, the devices require considerable effort from the parent/caregiver to ensure smooth operation," the report said.
Image: Child in car seat, via Shutterstock.