Hall Logic develops vehicle sensing technology to provide information to drivers, advanced driver assist systems, and autonomous driving systems. It currently offers a stand-alone gauge and phone app that uses engine information to calculate the weight of a vehicle’s load.
Products

Self-install Kit

Works with many automatic transmission vehicles built since 2006
 - Diagnostic port must run parallel to dash, does not work with CVT vehicles.
 - No tools needed: plug into your diagnostic port and secure the suction cup mount to the windshield.

HaulGauge readings are typically within 5% of actual weight. 
The first gauge reading occurs within a few seconds of driving, and accuracy improves as driving continues.