Is there something that could be hooked up to a car to see what's draining the battery?

Yes, a multimeter or a dedicated battery monitor can be connected to a car's battery to diagnose what's draining it. By measuring the current flow, these devices can help identify parasitic draws from components like lights, audio systems, or other electrical accessories. Additionally, a clamp meter can be used to measure current without disconnecting the battery, providing a convenient way to monitor power consumption in real-time.